644 Auto Electricity and Electronics
Copyright by Goodheart-Willcox Co., Inc.
Since hybrid gas-electric vehicles are now produced
and sold by many automakers, it is important that you
understand how these vehicles operate and the methods
for safely servicing them. The electrical/electronic service
methods you learned in previous chapters apply to hybrid
vehicles. The primary concern when working on a gas-
electric hybrid drive train is the extremely high voltage and
current stored and generated by the electric drive devices
and circuits. It is recommended that you take specialized
factory training before attempting to work on a hybrid. For
example, if you are going to work on a Ford hybrid, you
should attend a certifi ed Ford training program.
Please remember that the information in this chapter is
general and applies to all makes and models of hybrid vehi-
cles. You must refer to factory service instructions to effi ciently
and safely service hybrid vehicles. Even though hybrids can
be serviced with conventional tools and equipment, the speci-
fi cations, part locations, and repair methods will vary slightly.
Note: To identify a hybrid vehicle, look for
badging on the front fender, engine cover,
or hood. You can compare the vehicle’s VIN
(vehicle identifi cation number) to factory reference
information. The 5th, 6th, and 7th alphanumeric
characters in the VIN identify the vehicle.
Hybrid Problem Diagnosis
Hybrid vehicles have very extensive on-board diag-
nostic systems that will help you locate the source of
system problems. The on-board diagnostic system moni-
tors hundreds of operating conditions and will turn on one
or more warning lights if any monitored condition is not
within specifi cations. Figure 33-1 shows a few of the prob-
lems that can affect hybrid electric drive operation.
A hybrid ground fault interrupter constantly monitors
the system for high-voltage leakage into the metal chassis
of the vehicle. If high voltage from the HV battery pack or
motor-generator is shorting to frame ground, the ECU will
illuminate a warning light and de-energize the main power
relays (contactors) to disconnect the battery pack from its
electric drive circuit.
A glowing malfunction indicator light lets you know
that you should use a scan tool to retrieve stored trouble
codes. Figure 33-2 shows a hybrid drive trouble code
index chart. This chart explains what each code means and
where to go in the service information to fi nd instructions
for further testing.
Hybrid Service Safety
Modern gas-electric hybrid drive systems generate
enough electrical energy to cause electrocution. It takes
only a couple amps of current through your body to stop
your heart and kill you. Most hybrid vehicles conduct
almost 600 volts AC and 300 volts DC at hundreds of amps.
By comparison, home wall outlet voltage is 120 volts.
Therefore, it is important that you work safely when servic-
ing a hybrid vehicle. To work safely, you should:
Remove your jewelry.
Wear eye protection.
Wear insulating gloves.
Wear rubber-soled shoes.
Keep a fi re extinguisher nearby.
Follow towing safety procedures.
Disable the hybrid drive when working.
Set up a high-voltage buffer zone.
Remove the high-voltage disconnect.
Remove Jewelry
Remove all jewelry when working on a hybrid’s high-
voltage circuits. It is very easy for a metal watch to short
between a high-voltage conductor and ground since high
voltage can arc through the air and into the jewelry. The
high-voltage can instantly make the metal watch glow red
hot and burn deep into your wrist or arm. If a metal neck-
lace touches high-voltage conductors, it can weld itself to
the conductors. It will then glow red hot, begin to melt, and
may even explode in sparks of molten metal.
Wear Eye Protection
Make sure you wear safety glasses or goggles when
working on high-voltage hybrid components. If a high-voltage
cable shorts to ground, a violent electric arc will occur.
Figure 33-1. Note some of the problems you may encounter
when repairing a hybrid gas-electric drive train.
Powertrain
ECU Failure
Hybrid ECU
Failure
Drained or Shorted
HV Battery Pack
Loose or
Damaged
Power Cables
Power Control
Module Problems
Motor-
Generator
Problems
Hybrid Cooling
System Problems