654 Auto Electricity and Electronics
Copyright by Goodheart-Willcox Co., Inc.
problem with a particular component but the component tests
good, check for wiring problems in the corresponding circuit.
Use factory diagrams, like the one shown in Figure 33-16, to
locate any electric connector or other component that could
be affecting the operation of that circuit.
Summary
A hybrid vehicle VIN is located on the front fender,
engine cover, or hood. The 5th, 6th, and 7th alphanu-
meric characters in the VIN identify the hybrid vehicle.
Hybrid vehicles have extensive on-board diagnostic
systems that will help you locate the source of system
problems.
If the malfunction indicator light in a hybrid vehicle is
glowing, you should use a scan tool to retrieve stored
trouble codes.
Hybrid vehicles use a ground fault interrupter to
monitor the system for high-voltage leakage into the
metal chassis of the vehicle. If high-voltage leakage
is detected, the ECU will illuminate a warning light
and de-energize the main power relays (contactors) to
disconnect the HV battery pack from its drive circuit.
Some of the things you should do to safely service a hybrid
vehicle are remove your jewelry, wear eye protection, wear
insulating gloves, wear rubber-soled shoes, keep a fi re
extinguisher nearby, follow towing safety procedures, dis-
able the hybrid drive when working, set up a high-voltage
buffer zone, and remove the high-voltage disconnect.
After a period of extended service, the electrolyte and the
metal plates in an HV battery pack can become depleted.
When charging an HV battery pack, always follow the
battery charger and vehicle manufacturer instructions for
safely connecting the charger cables to the battery pack.
The most common reason for battery pack replace-
ment is physical damage, such as that incurred from a
severe collision.
To begin HV battery pack removal, remove the interior trim
or carpet over the battery. Then, unfasten the metal cover
and any ductwork that prevents battery pack removal.
To remove a battery pack, unbolt it from the vehicle as
required, and remove the large nuts or fasteners that secure
the high-voltage power cables to the battery pack.
When removing the HV battery pack, always wear
OSHA approved “lineman gloves” or gloves with an
approved insulation value of 1000 volts. Wrap electri-
cal tape around the metal terminals on the ends of the
orange power cables to prevent a high-voltage short.
The lugs of HV battery relays and contactors can often
become burned and pitted.
To make a pinpoint test on a high-voltage contactor,
remove or disconnect the HV battery pack. Then, measure
the resistance across the closed contactors with the igni-
tion key on and then off. Contactors should be replaced if
their resistance values are not within specifi cations.
Hybrid power cables can become damaged during a col-
lision or their metal ends can become loose or corroded.
To check the power cables, hook up a scan tool and
note the conductor resistance values of the high-
voltage circuit in the data list display. If these values
are not within specifi cations, tighten or repair the
cable ends or replace the hybrid power cables.
To check if the high-voltage power cables are leaking cur-
rent to the frame or ground body, touch your ohmmeter
test lead on one end of the cable terminal and connect the
other meter lead to frame or body ground. If the ohmmeter
reading is lower than specifi cations, the insulation may be
damaged and the cable should be replaced.
The component that most often fails in an air-cooled
system is the fan blower motor. In a water-cooled sys-
tem, the electric pump often fails.
To check an air-cooled system, listen for normal operation
of the cooling fan. To check a water-cooled system, place
a stethoscope on the electric pump to determine if it is
running when the hybrid is under a high electrical load.
To remove an inoperative cooling fan blower motor,
disconnect the wires and ducts before removing the
fasteners that secure the blower motor to the vehicle.
For a liquid system, you must disconnect the hoses and
wires going to the pump motor before replacement.
A lack of normal air or coolant fl ow can cause power con-
trol module overheating, which will set trouble codes.
When a scan tool shows a problem with a particular
component but the component tests good, check for
wiring problems in the corresponding circuit.
Review Questions—Chapter 33
Answer the following questions using the information
provided in this chapter.
1. What will happen if high voltage from the HV battery
pack or motor-generator is shorting to frame ground?
Figure 33-15. This motor rotor position sensor can only be ser-
viced after removing the motor-generator assembly from the
rear of the engine block.
Connector
Cylinder
Block
Sensor