Pinpoint Test I: One Or More Stoplamps Are Inoperative
Stoplamps
Pinpoint Test I: One Or More Stoplamps Are Inoperative
Refer to Wiring Diagram Set 90, Turn Signal/Stop/Hazard Lamps for schematic and connector information. Diagrams By Number
Normal Operation
When the brake pedal is applied, the stoplamp switch closes and routes voltage to the high mounted stoplamp and the multifunction switch through circuit 10 (LG/RD). The multifunction switch then routes the voltage through circuit 9 (LG/OG) to the LH rear lamp and circuit 5 (OG/LB) to the RH rear lamp. Ground for all the stoplamps is provided through circuit 57 (BK).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- High mounted stoplamp
- Multifunction switch
PINPOINT TEST I: ONE OR MORE STOPLAMPS ARE INOPERATIVE
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to Battery.
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I1 VERIFY THE INOPERATIVE STOPLAMP(S)
- Ignition OFF.
- Apply the brake pedal.
- Does the high mounted stoplamp illuminate?
Yes
GO to I4.
No
GO to I2.
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I2 CHECK CIRCUIT 10 (LG/RD) FOR AN OPEN (TO HIGH MOUNTED STOPLAMP)
- Disconnect: High Mounted Stoplamp C475.
- While applying the brake pedal, measure the voltage between the high mounted stoplamp C475-1, circuit 10 (LG/RD), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to I3.
No
REPAIR the circuit. TEST the system for normal operation.
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I3 CHECK CIRCUIT 57 (BK) FOR AN OPEN (HIGH MOUNTED STOPLAMP)
- Disconnect: Negative Battery Cable.
- Measure the resistance between the high mounted stoplamp C475-2, circuit 57 (BK), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new high mounted stoplamp. REFER to High Mounted Stoplamp Service and Repair. TEST the system for normal operation.
No
REPAIR the circuit. TEST the system for normal operation.
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I4 DETERMINE IF THE LH AND RH REAR STOPLAMPS ARE INOPERATIVE
NOTE: Make sure the multifunction switch is in the NEUTRAL position.
- Apply the brake pedal.
- Are both the LH and RH rear stoplamps inoperative?
Yes
GO to I5.
No
GO to I7.
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I5 CHECK CIRCUIT 10 (LG/RD) FOR AN OPEN (TO MULTIFUNCTION SWITCH)
- Disconnect: Multifunction Switch C202a.
- While applying the brake pedal, measure the voltage between the multifunction switch C202a-4, circuit 10 (LG/RD), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to I6.
No
REPAIR the circuit. TEST the system for normal operation.
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I6 CHECK CIRCUIT 57 (BK) FOR AN OPEN (BOTH REAR STOPLAMPS)
- Connect a fused jumper wire between the multifunction switch C202a-4, circuit 10 (LG/RD), harness side and the multifunction switch C202a-5, circuit 5 (OG/LB), harness side.
- Apply the brake pedal while observing the RH rear stoplamps.
- Do the RH rear stoplamps illuminate?
Yes
REMOVE the jumper wire. INSTALL a new multifunction switch. TEST the system for normal operation.
No
REMOVE the jumper wire. REPAIR the circuit. TEST the system for normal operation.
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I7 CHECK CIRCUIT 57 (BK) FOR AN OPEN (REAR STOPLAMP)
- Disconnect: Negative Battery Cable.
- Disconnect: Inoperative Stoplamp.
- Measure the resistance between the inoperative stoplamp, harness side and ground as follows:
- Is the resistance less than 5 ohms?
Yes
GO to I8.
No
REPAIR the circuit. TEST the system for normal operation.
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I8 CHECK THE MULTIFUNCTION SWITCH
- Disconnect: Multifunction Switch.
- Carry out the multifunction switch component test.
- Is the multifunction switch OK?
Yes
REPAIR circuit 9 (LG/OG) or circuit 5 (OG/LB) as necessary. TEST the system for normal operation.
No
INSTALL a new multifunction switch. TEST the system for normal operation.
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