Halderman J.D., Linder J. Automotive Fuel and Emissions Control Systems

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SCAN TOOLS AND ENGINE PERFORMANCE DIAGNOSIS 391

these tests can be run, the computer uses its internal diag-

nostic program to keep track of all the various conditions and

to schedule active tests so that they will not interfere with

each other.

OBD-II DRIVE CYCLE The vehicle must be driven under

a variety of operating conditions for all active tests to be per-

formed. A trip is defined as an engine-operating drive cycle

that contains the necessary conditions for a particular test to be

performed. For example, for the EGR test to be performed, the

engine has to be at normal operating temperature and deceler-

ating for a minimum amount of time. Some tests are performed

when the engine is cold, whereas others require that the vehicle

be cruising at a steady highway speed.

TYPES OF OBD-II CODES Not all OBD-II DTCs are of the

same importance for exhaust emissions. Each type of DTC has

different requirements for it to set, and the computer will turn

on the MIL only for emissions-related DTCs.

TYPE A CODES. A type A DTC is emission related and will cause

the MIL to be turned on at the first trip if the computer has

detected a problem. Engine misfire or a very rich or lean air–fuel

ratio, for example, would cause a typeA DTC. These codes alert

the driver to an emissions problem that may cause damage to

the catalytic converter.

TYPE B CODES. A type B code will be stored as a pending code

in the PCM, and the MIL will be turned on only after the second

consecutive trip, alerting the driver to the fact that a diagnostic

test was performed and failed.

NOTE: Type A and Type B codes are emission related

and will cause the lighting of the malfunction indicator

lamp, usually labeled “check engine” or “service engine

soon.”

TYPE C AND D CODES. Type C and type D codes are for use

with non-emission-related diagnostic tests. They will cause the

lighting of a “service” lamp (if the vehicle is so equipped).

OBD-II FREEZE-FRAME To assist the service techni-

cian, OBD-II requires the computer to take a “snapshot” or

freeze-frame of all data at the instant an emission-related

DTC is set. A scan tool is required to retrieve this data. CARB

and EPA regulations require that the controller store specific

freeze-frame (engine-related) data when the first emission

related fault is detected. The data stored in freeze-frame can

be replaced only by data from a trouble code with a higher

priority, such as a trouble related to a fuel system or misfire

monitor fault.

NOTE: Although OBD-II requires that just one freeze-

frame of data be stored, the instant an emission-related

DTC is set, vehicle manufacturers usually provide ex-

panded data about the DTC beyond that required. How-

ever, retrieving enhanced data usually requires the use

of an enhanced or factory-level scan tool.

P0727 Engine Speed Input Circuit No Signal

P0730 Incorrect Gear Ratio

P0731 Gear 1 Incorrect Ratio

P0732 Gear 2 Incorrect Ratio

P0733 Gear 3 Incorrect Ratio

P0734 Gear 4 Incorrect Ratio

P0735 Gear 5 Incorrect Ratio

P0736 Reverse Incorrect Ratio

P0740 Torque Converter Clutch System Problem

P0741 Torque Converter Clutch System Performance

or Stuck Off

P0742 Torque Converter Clutch System Stuck On

P0743 Torque Converter Clutch System Electrical

P0745 Pressure Control Solenoid Problem

P0746 Pressure Control Solenoid Performance or Stuck Off

P0747 Pressure Control Solenoid Stuck On

P0748 Pressure Control Solenoid Electrical

P0750 Shift Solenoid A Problem

P0751 Shift Solenoid A Performance or Stuck Off

P0752 Shift Solenoid A Stuck On

P0753 Shift Solenoid A Electrical

P0755 Shift Solenoid B Problem

P0756 Shift Solenoid B Performance or Stuck Off

P0757 Shift Solenoid B Stuck On

P0758 Shift Solenoid B Electrical

P0760 Shift Solenoid C Problem

P0761 Shift Solenoid C Performance or Stuck Off

P0762 Shift Solenoid C Stuck On

P0763 Shift Solenoid C Electrical

P0765 Shift Solenoid D Problem

P0766 Shift Solenoid D Performance or Stuck Off

P0767 Shift Solenoid D Stuck On

P0768 Shift Solenoid D Electrical

P0770 Shift Solenoid E Problem

P0771 Shift Solenoid E Performance or Stuck Off

P0772 Shift Solenoid E Stuck On

P0773 Shift Solenoid E Electrical

* The side of the engine where number one cylinder is located.

The vehicle computer must run tests on the various emission-

related components and turn on the malfunction indicator lamp

(MIL) if faults are detected. OBD-II is an active computer analy-

sis system because it actually tests the operation of the oxygen

sensors, exhaust gas recirculation system, and so forth when-

ever conditions permit. It is the purpose and function of the

PCM to monitor these components and perform these active

tests.

For example, the PCM may open the EGR valve momen-

tarily to check its operation while the vehicle is decelerating.

A change in the manifold absolute pressure (MAP) sensor

signal will indicate to the computer that the exhaust gas is, in

fact, being introduced into the engine. Because these tests

are active and certain conditions must be present before

OBD-II ACTIVE TESTS

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392 CHAPTER 30

The freeze-frame has to contain data values that occurred

at the time the code was set (these values are provided in stan-

dard units of measurement). Freeze-frame data is recorded dur-

ing the first trip on a two-trip fault. As a result, OBD-II systems

record the data present at the time an emission-related code is

recorded and the MIL activated. This data can be accessed and

displayed on a scan tool. Freeze-frame data is one frame or one

instant in time. Freeze-frame data is not updated (refreshed) if

the same monitor test fails a second time.

REQUIRED FREEZE-FRAME DATA ITEMS

쏋

Code that triggered the freeze-frame

쏋

A/F ratio, airflow rate, and calculated engine load

쏋

Base fuel injector pulse width

쏋

ECT, IAT, MAF, MAP, TP, and VS sensor data

쏋

Engine speed and amount of ignition spark advance

쏋

Open- or closed-loop status

쏋

Short-term and long-term fuel trim values

쏋

For misfire codes—identify the cylinder that misfired

NOTE: All freeze-frame data will be lost if the battery is

disconnected, power to the PCM is removed, or the scan

tool is used to erase or clear trouble codes.

DIAGNOSING INTERMITTENT MALFUNCTIONS Of all

the different types of conditions that you will see, the hardest

to accurately diagnose and repair are intermittent malfunc-

tions. These conditions may be temperature related (occur only

when the vehicle is hot or cold) or humidity related (occur only

when it is raining). Regardless of the conditions that will cause

the malfunction to occur, you must diagnose and correct the

condition.

When dealing with an intermittent concern, you should de-

termine the conditions when the malfunction occurs and then

try to duplicate those conditions. If a cause is not readily appar-

ent to you, ask the customer when the symptom occurs. Ask

if there are any conditions that seem to be related to or cause

the concern.

Another consideration when working on an OBD-II-

equipped vehicle is whether a concern is intermittent or

whether it only occurs when a specific diagnostic test is per-

formed by the PCM. Since OBD-II systems conduct diag-

nostic tests only under very precise conditions, some tests

may be run only once during an ignition cycle. Additionally,

if the requirements needed to perform the test are not met,

the test will not run during an ignition cycle. This type of on-

board diagnostics could be mistaken as “intermittent” when,

in fact, the tests are only infrequent (depending on how the

vehicle is driven). Examples of this type of diagnostic test are

S heaters, evaporative canister purge, catalyst efficiency,

and EGR flow. When diagnosing intermittent concerns on an

OBD-II-equipped vehicle, a logical diagnostic strategy is es-

sential. The use of stored freeze-frame information can also

be very useful when diagnosing an intermittent malfunction if

a code has been stored.

SERVICE/FLASH

PROGRAMMING

Designing a program that allows an engine to meet strict air

quality and fuel economy standards while providing excellent

performance is no small feat. However, this is only part of the

challenge facing engineers assigned with the task of develop-

ing OBD-II software. The reason for this is the countless vari-

ables involved with running the diagnostic monitors. Although

programmers do their best to factor in any and all operating

conditions when writing this complex code, periodic revisions

are often required.

Reprogramming consists of downloading new calibra-

tion files from a scan tool, personal computer (PC), or mo-

dem into the PCM’s electronically erasable programmable

read-only memory (EEPROM). This can be done on or off the

vehicle using the appropriate equipment. Since reprogram-

ming is not an OBD-II requirement however, many vehicles

will need a new PCM in the event software changes become

necessary. Physically removing and replacing the PROM chip

is no longer possible.

The following are three industry-standard methods used to

reprogram the EEPROM:

쏋

Remote programming

쏋

Direct programming

쏋

Off-board programming

REMOTE PROGRAMMING. Remote programming uses the scan

tool to transfer data from the manufacturer’s shop PC to the

vehicle’s PCM. This is accomplished by performing the follow-

ing steps:

쏋

Connect the scan tool to the vehicle’s DLC. 쎲 SEE

FIGURE 30–17.

쏋

Enter the vehicle information into the scan tool through

the programming application software incorporated in the

scan tool.

쎲 SEE FIGURE 30–18.

쏋

Download VIN and current EEPROM calibration using a

scan tool.

쏋

Disconnect the scan tool from the DLC and connect the

tool to the shop PC.

쏋

Download the new calibration from the PC to the scan

tool.

쎲 SEE FIGURE 30–19.

쏋

Reconnect the scan tool to the vehicle’s DLC and down-

load the new calibration into the PCM.

CAUTION: Before programming, the vehicle’s battery

must be between 11 and 14 volts. Do not attempt to pro-

gram while charging the battery unless using a special

battery charger that does not produce excessive ripple

voltage, such as the Midtronics PSC-300 (30 amp) or

PSC-550 (55 amp) or similar as specified by the vehicle

manufacturer.

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SCAN TOOLS AND ENGINE PERFORMANCE DIAGNOSIS 393

DIRECT PROGRAMMING. Direct programming does utilize a

connection between the shop PC and the vehicle DLC.

OFF-BOARD PROGRAMMING. Off-board programming is used if

the PCM must be programmed away from the vehicle. This is

preformed using the off-board programming adapter.

쎲 SEE

FIGURE 30–20.

J2534 REPROGRAMMING Legislation has mandated

that vehicle manufacturers meet the SAE J2534 standards

for all emissions-related systems on all new vehicles starting

with model year 2004. This standard enables independent

service repair operators to program or reprogram emissions-

related ECMs from a wide variety of vehicle manufacturers

witha single tool.

쎲 SEE FIGURE 30–21. A J2534-compliant

FIGURE 30–18 Follow the on-screen instructions.

FIGURE 30–19 An Internet connection is usually needed to

perform updates, although some vehicle manufacturers use

CDs that are updated regularly at a cost to the shop.

FIGURE 30–20 Connecting cables and a computer to perform

off-board programming.

FIGURE 30–17 The first step in the reprogramming procedure

is to determine the current software installed using a scan

tool. Not all scan tools can be used. In most cases using the

factory scan tool is needed for reprogramming unless the scan

tool is equipped to handle reprogramming.

pass-through system is a standardized programming and

diagnostic system. It uses a PC plus a standard interface

to a software device driver and a hardware vehicle com-

munication interface. The interface connects to a PC and to

a programmable ECM on a vehicle through the J1962 data

link connector (DLC). This system allows programming of all

vehicle manufacturer ECMs using a single set of program-

ming hardware. Programming software made available by

the vehicle manufacturer must be functional with a J2534-

compliant pass-through system.

The software for a typical pass-through application

consists of two major components, including the following:

쏋

The part delivered by the company that furnishes the hard-

ware for J2534 enables the pass-through vehicle communi-

cation interface to communicate with the PC and provides

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394 CHAPTER 30

Task Force (NASTF) website for the addresses for all

vehicle manufacturers’ service information and cost,

www.NASTF.org.

Since the majority of vehicle manufacturers make this software

available in downloadable form, having an Internet browser

(Explorer/Netscape) and connection is a must.

DLC

SAE J2534

PASS-THROUGH

DEVICE

PC CABLE

VEHICLE

CABLE

MODULE

PROGRAMMING

INTERNET

FIGURE 30–21 The J2534 pass-through reprogramming

system does not need a scan tool to reflash the PCM on most

2004 and newer vehicles.

FIGURE 30–22 A typical J2534 universal reprogrammer that

uses the J2534 standards.

for all Vehicle Communication Protocols as required by

SAE J2534. It also provides for the software interface to

work with the software applications as provided for by the

vehicle manufacturers.

쎲 SEE FIGURE 30–22.

쏋

The second part of the pass-through enabling software is

provided for by the vehicle manufacturers. This is normally

a subset of the software used with their original equipment

manufacturer (OEM) tools, and their website will indicate

how to obtain this software and under what conditions

it can be used. Refer to the National Automotive Service

MANUFACTURER’S

DIAGNOSTIC ROUTINES

Each vehicle manufacturer has established its own diagnostic

routines and they should be followed. Most include the following

steps:

STEP 1 Retrieve DTCs.

STEP 2 Check for all technical service bulletins that could be

related to the stored DTC.

STEP 3 If there are multiple DTCs, the diagnostic routine may

include checking different components or systems in-

stead of when only one DTC was stored.

STEP 4 Perform system checks.

STEP 5 Perform the necessary service or repair

STEP 6 Perform a road test matching the parameters re-

corded in the freeze-frame to check that the repair has

corrected the malfunction.

STEP 7 Repeat the road test to cause the MIL to be

extinguished.

NOTE: Do not clear codes (DTCs) unless instructed by

the service information.

Following the vehicle manufacturer’s specific diagnostic

routines will ensure that the root cause is found and the repair

verified. This is important for customer satisfaction.

After the repair has been successfully completed, the vehicle

should be driven under similar conditions that caused the origi-

nal concern. Verify that the problem has been corrected. To

perform this test drive, it is helpful to have a copy of the freeze-

frame parameters that were present when the DTC was set. By

driving under similar conditions, the PCM may perform a test

of the system and automatically extinguish the MIL. This is the

method preferred by most vehicle manufacturers. The DTC can

be cleared using a scan tool, but then that means that monitors

will have to be run, and the vehicle may fail an emission inspec-

tion if driven directly to the testing station.

COMPLETING

SYSTEM REPAIRS

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SCAN TOOLS AND ENGINE PERFORMANCE DIAGNOSIS 395

The PCM can be reset or cleared of previously set DTCs and

freeze-frame data in the following ways:

1. Driving the vehicle. Drive the vehicle under similar condi-

tions that were present when the fault occurred. If the condi-

tions are similar and the PCM performed the noncontinuous

monitor test and it passed three times, then the PCM will

extinguish the MIL. This is the method preferred by most

vehicle manufacturers, however, this method could be time

consuming. If three passes cannot be achieved, the owner

of the vehicle will have to be told that even though the check

engine light (MIL) is on, the problem has been corrected,

and the MIL should go out in a few days of normal driving.

2. Clear DTCs using a scan tool. A scan tool can be used

to clear the DTC, which will also delete all of the freeze-

frame data. The advantage of using a scan tool is that the

check engine (MIL) will be out and the customer will be

happy that the problem (MIL on) has been corrected. Do

not use a scan tool to clear a DTC if the vehicle is going

to be checked soon at a test station for state-mandated

emission tests.

3. Battery disconnect. Disconnecting the negative battery ca-

ble will clear the DTCs and freeze-frame on many vehicles but

not all. Besides clearing the DTCs, disconnecting the battery

for about 20 minutes will also erase radio station presets and

other memory items in many cases. Most vehicle manufac-

turers do not recommend that the battery be disconnected to

clear DTCs, and it may not work on some vehicles.

PROCEDURES FOR

RESETTING THE PCM

ROAD TEST (DRIVE CYCLE)

Use the freeze-frame data and test-drive the vehicle so that

the vehicle is driven to match the conditions displayed on the

freeze-frame. If the battery has been disconnected, then the

vehicle may have to be driven under conditions that allow

thePCM to conduct monitor tests. This drive pattern is called a

The Brake Pedal Trick

If the vehicle manufacturer recommends that battery

power be disconnected, first disconnect the nega-

tive battery cable and then depress the brake pedal.

Because the brake lights are connected to battery

power, depressing the brake pedal causes all of the

capacitors in the electrical system and computer(s)

to discharge through the brake lights.

TECH TIP

Drive the Light Out

If working on a vehicle that is subject to state emission

testing, it is best to not clear codes. When diagnostic

trouble codes (DTCs) are cleared, all of the monitors

have to be rerun, and this can be a time-consuming job.

Instead of clearing the code, simply drive the vehicle un-

til the PCM clears the code. This will likely take less time

compared to trying to drive the vehicle under varying

conditions to run all of the monitors.

TECH TIP

drive cycle. The drive cycle is different for each vehicle manu-

facturer, but a universal drive cycle may work in many cases. In

many cases performing a universal drive cycle will reset most

monitors in most vehicles.

UNIVERSAL DRIVE CYCLE

PRECONDITIONING: Phase 1

MIL must be off.

No DTCs present.

Fuel fill between 15% and 85%.

Cold start—Preferred = 8-hour soak at 68°F to 86°F.

Alternative = ECT below 86°F.

1. With the ignition off, connect scan tool.

2. Start engine and drive between 20 and 30 mph for 22 min-

utes, allowing speed to vary.

3. Stop and idle for 40 seconds, gradually accelerate to 55 mph.

4. Maintain 55 mph for 4 minutes using a steady throttle input.

5. Stop and idle for 30 seconds, then accelerate to 30 mph.

6. Maintain 30 mph for 12 minutes.

7. Repeat steps 4 and 5 four times.

Using scan tool, check readiness. If insufficient readiness

set, continue to universal drive trace phase II.

Important: (Do not shut off engine between phases).

Phase II:

1. Vehicle at a stop and idle for 45 seconds, then accelerate

to 30 mph.

2. Maintain 30 mph for 22 minutes.

3. Repeat steps 1 and 2 three times.

4. Bring vehicle to a stop and idle for 45 seconds, then

accelerate to 35 mph.

5. Maintain speed between 30 and 35 mph for 4 minutes.

6. Bring vehicle to a stop and idle for 45 seconds, then

accelerate to 30 mph.

7. Maintain 30 mph for 22 minutes.

8. Repeat steps 6 and 7 five times.

9. Using scan tool, check readiness.

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396 CHAPTER 30

2. A thorough visual inspection is important during the

diagnosis and troubleshooting of any engine performance

problem or electrical malfunction.

3. If the MIL is on, retrieve the DTC and follow the manufac-

turer’s recommended procedure to find the root cause of

the problem.

4. OBD-II vehicles use a 16-pin DLC and common DTCs.

SUMMARY

1. Funnel diagnostics—Visual approach to a diagnostic

procedure:

Step 1 Verify the problem (concern)

Step 2 Perform a thorough visual inspection and basic tests

Step 3 Retrieve the diagnostic trouble codes (DTCs)

Step 4 Check for technical service bulletins (TSBs)

Step 5 Look carefully at scan tool data

Step 6 Narrow the problem to a system or cylinder

Step 7 Repair the problem and determine the root cause

Step 8 Verify the repair and check for any stored DTCs

1. Explain the procedure to follow when diagnosing a vehicle

with stored DTCs using a scan tool.

2. Discuss what the PCM does during a drive cycle to test

emission-related components.

3. Explain the difference between a type A and type B OBD-II

DTC.

4. List three things that should be checked as part of a thor-

ough visual inspection.

5. List the eight-step funnel diagnostic procedure.

6. Explain why a bulletin search should be performed after

stored DTCs are retrieved.

7. List the three methods that can be used to reprogram a PCM.

1. Technician A says that the first step in the diagnostic proc-

ess is to verify the problem (concern). Technician B says

the second step is to perform a thorough visual inspection.

Which technician is correct?

a. Technician A only c. Both Technicians A and B

b. Technician B only d. Neither Technician A nor B

2. Which item is not important to know before starting the

diagnosis of an engine performance problem?

a. List of previous repairs

b. The brand of engine oil used

c. The type of gasoline used

d. The temperature of the engine when the problem occurs

3. A paper test can be used to check for a possible problem

with ______________.

a. The ignition system (bad spark plug wire)

b. A faulty injector on a multiport engine

c. A burned valve

d. All of the above

4. Which step should be performed last when diagnosing an

engine performance problem?

a. Checking for any stored diagnostic trouble codes (DTCs)

b. Checking for any technical service bulletins (TSBs)

c. Performing a thorough visual inspection

d. Verify the repair

5. Technician A says that if the opposite DTC can be set, the

problem is the component itself. Technician B says if the

opposite DTC cannot be set, the problem is with the wiring

or grounds. Which technician is correct?

a. Technician A only c. Both Technicians A and B

b. Technician B only d. Neither Technician A nor B

6. The preferred method to clear DTCs is to ______________.

a. Disconnect the negative battery cable for 10 seconds

b. Use a scan tool

Remove the computer (PCM) power feed fuse

d. Cycle the ignition key on and off 40 times

7. Which is the factory scan tool for Chrysler brand vehicles

equipped with CAN?

a. Star Scan c. NGS

b. Tech 2 d. Master Tech

8. Technician A says that reprogramming a PCM using the

J2534 system requires a factory scan tool. Technician B

says that reprogramming a PCM using the J2534 system

requires Internet access. Which technician is correct?

a. Technician A only

b. Technician B only

c. Both Technicians A and B

d. Neither Technician A nor B

9. Technician A says that knowing if there are any stored

DTCs may be helpful when checking for related TSBs.

Technician B says that only a factory scan tool should be

used to retrieve DTCs. Which technician is correct?

a. Technician A only

b. Technician B only

c. Both Technicians A and B

d. Neither Technician A nor B

10. Which method can be used to reprogram a PCM?

a. Remote c. Off-board

b. Direct d. All of the above

REVIEW QUESTIONS

CHAPTER QUIZ

M30_HALD2920_03_SE_CH30.indd 396 15/12/10 6:09 PM

HYBRID SAFETY AND SERVICE PROCEDURES 397

chapter

OBJECTIVES: After studying Chapter 31 , the reader should be able to: • Safely depower a hybrid electric vehicle. • Safely

perform high-voltage disconnects. • Understand the unique service issues related to HEV high-voltage systems. • Correctly

use appropriate personal protective equipment (PPE). • Perform routine vehicle service procedure on a hybrid electric vehicle.

• Explain hazards while driving, moving, and hoisting a hybrid electric vehicle.

KEY TERMS: ANSI 397 • ASTM 397 • CAT III 398 • DMM 398 • Floating ground 400 • HV 397 • HV cables 397

• IEC 398 • Lineman’s gloves 397 • NiMH 403 • OSHA 397 • Service plug 401

NEED FOR CAUTION There have been electrical systems

on vehicles for over 100 years. Technicians have been repair-

ing vehicle electrical systems without fear of serious injury

or electrocution. However, when working with hybrid electric

vehicles, this is no longer true. It is now possible to be seriously

injured or electrocuted (killed) if proper safety procedures are

not followed.

Hybrid electric vehicles and all electric vehicles use high-

voltage ( HV ) circuits that if touched with an unprotected hand

could cause serious burns or even death.

IDENTIFYING HIGH-VOLTAGE CIRCUITS High-voltage

cables are identified by color of the plastic conduit and include

the following:



Blue or yellow. 42 volts (not a shock hazard but an arc

will be maintained if a circuit is opened)



Orange. 144 to 600 volts or higher

RUBBER GLOVES Before working on the high-voltage

system of a hybrid electric vehicle, be sure that high-voltage

lineman’s gloves are available. Be sure that the gloves are

rated at least 1,000 volts and class “0” by ANSI/ASTM. The

American National Standards Institute (ANSI) is a private,

nonprofit organization that administers and coordinates the U.S.

voluntary standardization and conformity assessment system.

ASTM International, originally known as the American Society

for Testing and Materials ( ASTM ), was formed over a century

ago to address the need for component testing in industry.

The Occupational Safety and Health Administration (OSHA)

requirements specify that the HV gloves get inspected every six

months by a qualified glove inspection laboratory. Use an outer

leather glove to protect the HV rubber gloves. Inspect the gloves

carefully before each use. High voltage and current (amperes) in

combination is fatal.

 SEE FIGURES 31–1 AND 31–2 .

NOTE: The high-voltage insulated safety gloves must be

recertified every six months to remain within Occupational

Safety and Health Administration (OSHA) guidelines.

Before using the rubber gloves, they should be tested for

leaks using the following procedure:

1. Roll the glove up from the open end until the lower portion

of the glove begins to balloon from the resulting air pres-

sure. Be sure to “lean” into the sealed glove to raise the

internal air pressure. If the glove leaks any air, discard the

gloves.

 SEE FIGURE 31–3 .

2. The gloves should not be used if they show any signs of

wear and tear.

HYBRID SAFETY

AND SERVICE PROCEDURES

HIGH-VOLTAGE

SAFETY

Touching circuits or wires containing high voltage

can cause severe burns or death.

WARNING

HIGH-VOLTAGE

SAFETY EQUIPMENT

398 CHAPTER 31

C A T I Typically a CAT I meter is used for low-voltage mea-

surements, such as voltage measurements at wall

outlets in the home. Meters with a CAT I rating are

usually rated at 300 to 800 volts. CAT I is for relatively

low-energy levels, and while the voltage level to be

high enough for use when working on a hybrid electric

vehicle, the protective energy level is lower than what

is needed.

CAT II A higher-rated meter that would be typically used for

checking voltages at the circuit-breaker panel in the

home. Meters with a CAT II rating are usually rated at

300 to 600 volts. CAT II rated meters have similar volt-

age ratings as the other CAT ratings, but the energy

level of protection is higher with a CAT II compared to

a CAT I.

CAT III CAT III is the minimum-rated meter that should be

used for hybrid vehicles. Meters with a CAT III rating

are usually rated at 600 to 1,000 volts and the highest

energy level that is needed to protect the service tech-

nician.

CAT IV CAT IV meters are for clamp-on meters only. A clamp-

on meter is used to measure current (amperes) in a

circuit by placing the clamp around the wire carrying

the current. If a clamp-on meter also has meter leads

for voltage measurements, that part of the meter will

be rated as CAT III.

INSULATION TESTER An electrical insulation tester,

such as the Fluke 1587, is used to test for electrical continuity

between the high-voltage wires or components and the body

of the vehicle. If a hybrid electric vehicle has been involved in

any type of collision or any other incident where damage could

occur to the insulation, the high-voltage system should be

checked. An insulation tester is more expensive than a digital

meter. This means that an individual service technician often

does not purchase one, but any technician or service shop that

works on hybrid electric vehicles should have one available.

FIGURE 31–1 Rubber lineman’s gloves protect the wearer

from a shock hazard.

CAT III-RATED DIGITAL MULTIMETER Hybrid electric

vehicles are equipped with electrical systems whose voltages

can exceed 600 volts DC. A CAT III-certified digital multimeter

(DMM) is required for making measurements on these high-

voltage systems.

The International Electrotechnical Commission (IEC)

has several categories of voltage standards for meter and meter

leads. These categories are ratings for over-voltage protection

and are rated CAT I, CAT II, CAT III, and CAT IV. The higher the

category (CAT) rating, the greater the protection to the tech-

nician when measuring high-energy voltage. Under each cat-

egory there are various voltage ratings:

FIGURE 31–2 Wearing leather gloves over the lineman’s

gloves helps protect the rubber gloves from damage.

FIGURE 31–3 Checking rubber lineman’s gloves for

pinhole leaks.

Cables and wiring are orange in color. High-

voltage insulated safety gloves and a face shield

must be worn when carrying out any diagnostics

involving the high-voltage systems or components.

WARNING

HYBRID SAFETY AND SERVICE PROCEDURES 399

LOCATIONS WHERE SHOCKS CAN OCCUR Accidental

and unprotected contact with any electrically charged (“hot”

or “live”) high-voltage component can cause serious injury or

death. However, receiving an electric shock from a hybrid vehi-

cle is highly unlikely because of the following:

1. Contact with the battery module or other components in-

side the battery box can occur only if the box is damaged

and the contents are exposed or the box is opened without

following proper precautions.

2. Contact with the electric motor can occur only after one or

more components are removed.

3. The high-voltage cables can be easily identified by their

distinctive orange color, and contact with them can be

avoided.

4. The system main relays (SMRs) disconnect power from the

cables the moment the ignition is turned off.

LOCATIONS OF AUXILIARY BATTERIES  SEE

CHART 31–1 for a summary of the locations of auxiliary batteried.

EYE PROTECTION Eye protection should be worn when test-

ing for high voltage, which is considered by many experts to be

over 60 volts. Eye protection should include the following features:

1. Plastic frames (avoid metal frames as these are conductive

and could cause a shock hazard)

2. Side shields

3. Meet the standard ANSI Z87.1

Most hybrid electric systems use voltages higher than this

threshold. If the system has not been powered down or has not

had the high-voltage system disabled, a shock hazard is always

possible. Even when the high-voltage system has been discon-

nected, there is still high voltage in the HV battery box.

NOTE: Some vehicle manufactures specify that full face

shields be worn instead of safety glasses when working

with high voltage circuits or components.

SAFETY CONES Ford requires that cones be placed at the

four corners of any hybrid electric vehicle when service work on

the high voltage system is being performed. They are used to

establish a safety zone around the vehicles so that other techni-

cians will know that a possible shock hazard may be present.

FIGURE 31–5 The meter leads should also be CAT III rated

when checking voltages on a hybrid electric vehicle.

Is It the Voltage Rating That Determines the

CAT Rating?

Yes and no. The voltages stated for the various CAT

ratings are important, but the potential harm to a

technician due to the energy level is what is most im-

portant. For example, some CAT II-rated meters may

have a stated voltage higher than a meter that has

a CAT III rating. Always use a meter that has a CAT

III rating when working on a hybrid electric vehicle.

 SEE FIGURES 31–4 AND 31–5 .

FREQUENTLY ASKED QUESTION

FIGURE 31–4 Be sure to only use a meter that is CAT III

rated when taking electrical voltage measurements on a hybrid

electric or electric vehicle.

ELECTRIC SHOCK

POTENTIAL

THE NEED TO DEPOWER THE HV SYSTEM During rou-

tine vehicle service work there is no need to go through any pro-

cedures needed to depower or to shut off the high-voltage circuits.

DEPOWERING THE

HIGH-VOLTAGE SYSTEM

FIBERGLASS POLE Ford requires that a ten foot insulated

fiberglass pool be available outside the safety zone to be used

to pull a technician away from the vehicle in the unlikely event

of an accident where the technician is shocked or electrocuted.

400 CHAPTER 31

FIGURE 31–6 The Ford Escape Hybrid instrument panel

showing the vehicle in park and the tachometer on “EV” in-

stead of 0 RPM. This means that the gasoline engine could

start at any time depending on the state-of-charge of the high-

voltage batteries and other factors.

CHART 31–1

As a rule of thumb, the auxiliary battery is usually a flood type if it is located under the hood and an AGM type if it is in the trunk area.

HYBRID VEHICLE AUXILIARY BATTERY CHART

VEHICLE AUXILIARY BATTERY TYPE AUXILIARY BATTERY LOCATION

Honda Insight Hybrid Flooded lead acid Underhood; center near bulkhead

Honda Civic Hybrid Flooded lead acid Underhood; driver’s side

Honda Accord Hybrid Flooded lead acid Underhood; driver’s side

Ford Escape Hybrid Flooded lead acid Underhood; driver’s side

Toyota Prius Hybrid (2001–2003) Absorbed glass mat (AGM) Trunk; driver’s side

Toyota Prius Hybrid (2004–2007) Absorbed glass mat (AGM) Trunk; passenger side

Toyota Highlander Hybrid Flooded lead acid Underhood; passenger side

Toyota Camry Hybrid Absorbed glass mat (AGM) Trunk; passenger side

Lexus RX 400h Hybrid Flooded lead acid Underhood; passenger side

Lexus GS 450h Hybrid Absorbed glass mat (AGM) Trunk; driver’s side

Chevrolet/GMC Hybrid Pickup Truck Flooded lead acid Underhood; driver’s side

Silence Is NOT Golden

Never assume the vehicle is shut off just because the

engine is off. When working with a Toyota or Lexus

hybrid electric vehicle, always look for the READY in-

dicator status on the dash display. The vehicle is shut

off when the READY indicator is off.

The vehicle may be powered by the following:

1. The electric motor only

2. The gasoline engine only

3. A combination of both the electric motor and the

gasoline engine

The vehicle computer determines the mode in

which the vehicle operates to improve fuel economy

and reduce emissions. The driver cannot manually

select the mode.

 SEE FIGURE 31–6 .

TECH TIP

High Voltage Is Insulated from the Vehicle Body

Both positive and negative high-voltage power cables

are isolated from the metal chassis, so there is no

possibility of shock by touching the metal chassis.

This design is called a floating ground .

A ground fault monitor continuously monitors for

high-voltage leakage to the metal chassis while the

vehicle is running. If a malfunction is detected, the

vehicle computer will illuminate the master warning

light in the instrument cluster and the hybrid warning

light in the LCD display. The HV battery pack relays

will automatically open to stop electricity flow in a

collision sufficient to activate the SRS air bags.

TECH TIP

Power remains in the high-voltage electrical

system for up to 10 minutes after the HV battery

pack is shut off. Never touch, cut, or open any

orange high-voltage power cable or high-voltage

component without confirming that the high-

voltage has been completely discharged.

WARNING