Caution!
When measuring high voltage levels in a gas-
electric hybrid drive with a VOM, use a high-
voltage meter with test leads having thick
insulation. If you use a conventional VOM and
test leads, they can be damaged by the high
voltage in the hybrid system.
Servicing Hybrid Power Cables
The hybrid power cables are normally trouble free.
However, they can become damaged during a collision or
their metal ends can become loose or corroded. Some
high-voltage cables have special watertight terminal
ends, Figure 38-29. However, most hybrids use an eye-
type connector that is secured to a threaded metal stud
with a nut.
To check the power cables, note conductor resistance
values of the high-voltage circuit in the data list display
of your scan tool. If these values are not within specs,
tighten or repair the cable ends or replace the hybrid
power cables if needed.
If your scan tool reading shows a ground fault
problem with the cables, they may be leaking current to
frame or body ground. 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 specs (usually around 350k ohms), the insula-
tion may be leaking high voltage to ground and the cable
should be replaced. See Figure 38-30.
A loose cable end can overheat and burn the electrical
connection. Always torque the hybrid cable fasteners to
factory specifications using a torque wrench to ensure the
connection is not too loose or too tight.
To replace a high-voltage power cable, disconnect
both ends of the cable. Remove the clips that secure the
power cable to the vehicle. Finally, install the new power
cable in reverse order of removal.
Servicing Power Control Module
A trouble code will normally be set when problems
develop in the power control module. Sometimes a cir-
cuit board in the power control module will fail and
require replacement. A lack of normal air or coolant flow
can cause power control module overheating, which will
also set trouble codes.
Some hybrid vehicles use separate converters. For
example, Figure 38-31 shows a dc-to-dc converter that
mounts in the engine compartment. If your scan tool indi-
cates internal converter problems, the defective converter
should be removed and replaced.
Servicing the Hybrid Cooling System
If the hybrid cooling system fails, components in the
hybrid drive system can overheat. Trouble codes that
indicate the components or circuits at fault will be set. If
the system is air cooled, listen for normal operation of the
cooling fan. If the system is water cooled, place a stetho-
scope on the electric pump to determine if it is running
when the hybrid is under a high electrical load.
If you find an inoperative cooling fan blower motor,
replace it as you would a climate control blower.
Disconnect the wires and ducts before removing the fas-
teners that secure the blower motor to the vehicle. See
716 Section 5 Electrical Systems
Figure 38-29. This power cable has a waterproof terminal end.
O-ring seals on the power control module or the motor-gener-
ator housing keep water out of the system.
Figure 38-30. By connecting an ohmmeter between each drive
cable and ground, you can find any cable that is leaking
voltage.The cable’s insulation may have broken down, allowing
small amounts of current to leak out of the circuit. (Toyota)
KΩ