Toyota Highlander Service Manual: Electronic circuit inspection procedure
1. BASIC INSPECTION
(a) RESISTANCE MEASURING CONDITION OF ELECTRONIC PARTS
- Unless stated, all resistance is measured at an ambient
temperature of 20 C (68 F). Resistances
measured may be outside the specifications if measured at high temperatures,
i.e. immediately
after the vehicle has been running. Measurements should be made after the
engine
has cooled down.
(b) HANDLING CONNECTORS
- When disconnecting a connector, first squeeze the
mating halves tightly together to release the lock,
then press the lock claw and separate the connector.
- When disconnecting a connector, do not pull on the
harnesses. Grasp the connector directly and separate
it.
- Before connecting the connector, check that there
are no deformed, damaged, loose or missing terminals.
- When connecting a connector, press firmly until you
hear the lock close with a "click" sound.
- If checking the connector with a TOYOTA electrical
tester, check it from the backside (harness side) of
the connector using a mini test lead.
NOTICE:
As a waterproof connector cannot be checked from
the backside, check by connecting a sub-harness.
Do not damage the terminals by moving the inserted
tester needle.
(c) CHECKING CONNECTORS
- Checking when the connector is connected:
Squeeze the connector together to confirm that it is
fully inserted and locked.
- Checking when the connector is disconnected:
Check by pulling the wire harness lightly from the
backside of the connector. Look for unlatched terminals,
missing terminals, loose crimps or broken conductor
wires.
Check visually for corrosion, metallic or foreign objects
and water; and bent, rusted, overheated, contaminated,
and deformed terminals.
NOTICE:
When testing a gold-plated female terminal, always use a
gold-plated male terminal.
- Checking the contact pressure of the terminal:
Prepare a spare male terminal. Insert it into a female
terminal, and check for good tension when inserting
and after full engagement
(d) REPAIR METHOD OF CONNECTOR TERMINAL
- If there is any dirt on the terminal, clean the contact
point using an air gun or shop rag. Never polish the
contact point using sandpaper as the platings may
come off.
- If there is abnormal contact pressure, replace the
female terminal. If the male terminal is gold-plated
(gold color), use a gold-plated female terminal; if it
is silver-plated (silver color), use a silver-plated female
terminal.
- Damaged, deformed, or corroded terminals should
be replaced. If the terminal will not lock into the
housing, the housing may have to be replaced.
(e) HANDLING OF WIRE HARNESS
- If removing a wire harness, check the wiring and
clamping before proceeding so that it can be restored
in the same way.
- Never twist, pull or slacken the wire harness more
than necessary.
- Never make the wire harness come into contact
with a high temperature part, rotating, moving, vibrating
or sharp-edged parts. Avoid panel edges,
screw tips and similar sharp items.
- When installing parts, never pinch the wire harness.
- Never cut or break the cover of the wire harness. If
it is cut or broken, replace it or securely repair it with
vinyl tape.
2. CHECK OPEN CIRCUIT
(a) For an open circuit in the wire harness in Fig. 1, perform
a resistance check (step b) or a voltage check (step c).
(b) Check the resistance.
- Disconnect connectors A and C and measure the
resistance between them.
Resistance: Below 1 W
HINT:
Measure the resistance while lightly shaking the wire harness
vertically and horizontally.
Fig. 2:
Tester Connection |
Specified Condition |
Connector A terminal 1 -
Connector C terminal |
10 kW or higher |
Connector A terminal 2 -
Connector C terminal 2 |
Below 1 kW |
If your results match the examples above, an open circuit exists
between terminal 1 of connector A and terminal 1 of connector
C.
- Disconnect connector B and measure the resistance
between the connectors.
Fig. 3:
Tester Connection |
Specified Condition |
Connector A terminal 1 -
Connector B1 terminal 1 |
Below 1 kW |
Connector B2 terminal 1 -
Connector C terminal 1 |
10 kW or higher |
If your results match the examples above, an open circuit exists
between terminal 1 of connector B2 and terminal 1 of connector
C.
(c) Check the voltage.
- In a circuit in which voltage is applied to the ECU
connector terminal, an open circuit can be checked
by conducting a voltage check.
Fig. 4:
With each connector still connected, measure the
voltage between the body ground these terminals
(in this order): 1) terminal 1 of connector A at the
ECU 5V output terminal, 2) terminal 1 of connector
B, and 3) terminal 1 of connector C.
- Example results:
If your results match the examples above, an open circuit exists
in the wire harness between terminal 1 of B and terminal 1 of
C.
3. CHECK SHORT CIRCUIT
(a) If the wire harness is ground shorted (Fig. 5), locate the
section by conducting a resistance check with the body
ground (below).
(b) Check the resistance with the body ground.
- Disconnect connectors A and C and measure the
resistance between terminals 1 and 2 of connector
A and the body ground.
Resistance: 10 kW or higher
HINT:
Measure the resistance while lightly shaking the wire harness
vertically and horizontally.
Fig. 6:
If your results match the examples above, a short circuit exists
between terminal 1 of connector A and terminal 1 of connector
C.
- Disconnect connector B and measure the resistance
between terminal 1 of connector A and the
body ground, and terminal 1 of connector B2 and
the body ground.
Fig. 7:
If your results match the examples above, a short
circuit exists between terminal 1 of connector B2
and terminal 1 of connector C.
4. CHECK AND REPLACE ECU
NOTICE:
- The connector should not be disconnected from the
ECU. Perform the inspection from the backside of the
connector on the wire harness side.
- When no measuring condition is specified, perform
the inspection with the engine stopped and the ignition
switch ON.
- Check that the connectors are fully seated. Check for
loose, corroded or broken wires.
(a) First check the ECU ground circuit. If it is faulty, repair it.
If it is normal, the ECU could be faulty. Replace the ECU
with a normal functioning one and check if the symptoms
occur. If the trouble symptoms stop, replace the ECU.
- Measure the resistance between the ECU ground
terminal and body ground.
Resistance: Below 1 W
- Disconnect the ECU connector. Check the ground
terminals (on the ECU side and wire harness side)
for evidence of bending, corrosion or foreign material.
Lastly check the contact pressure of the female
terminals.
How to read and use each page is shown below.
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