Pinpoint Test I: One Or More Stoplamps Are Inoperative
Stoplamps
Pinpoint Tests
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 routes voltage to the multifunction switch and the circuit filter through circuit 10 (LG/RD). The multifunction switch then routes the voltage through circuits 9 (LG/OG) and 5 (OG/LB) to the LH and RH rear lamps, and the circuit filter routes the voltage to the high mounted stoplamp through circuit 511 (LG). Ground for all the stoplamps is provided through circuit 57 (BK).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Circuit filter
- 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 I6.
No
GO to I2.
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I2 CHECK FOR VOLTAGE TO THE HIGH MOUNTED STOPLAMP
- Disconnect: High Mounted Stoplamp C904.
- While applying the brake pedal, measure the voltage between the high mounted stoplamp C904-1, circuit 511 (LG), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to I3.
No
GO to I4 .
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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 C904-2, 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 CHECK CIRCUIT 10 (LG/RD) FOR AN OPEN (TO CIRCUIT FILTER)
- Disconnect: Circuit Filter C3148.
- While applying the brake pedal, measure the voltage between the circuit filter C3148-1, circuit 10 (LG/RD), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to I5.
No
REPAIR the circuit. TEST the system for normal operation.
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I5 CHECK CIRCUIT 511 (LG) FOR AN OPEN
- Measure the resistance between the high mounted stoplamp C904-1, circuit 511 (LG), harness side and the circuit filter C3148-3, circuit 511 (LG), harness side.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new circuit filter. TEST the system for normal operation.
No
REPAIR the circuit. TEST the system for normal operation.
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I6 DETERMINE IF BOTH 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 I7.
No
GO to I9.
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I7 CHECK CIRCUIT 10 (LG/RD) FOR AN OPEN (TO MULTIFUNCTION SWITCH)
- Disconnect: Multifunction Switch C202c.
- While applying the brake pedal, measure the voltage between the multifunction switch C202c-4, circuit 10 (LG/RD), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to I8.
No
REPAIR the circuit. TEST the system for normal operation.
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I8 CHECK CIRCUIT 57 (BK) FOR AN OPEN (BOTH REAR STOPLAMPS)
- Connect a fused jumper wire between the multifunction switch C202c-4, circuit 10 (LG/RD), harness side and the multifunction switch C202c-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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I9 CHECK FOR VOLTAGE TO THE REAR STOPLAMP
- Disconnect: Inoperative Stoplamp.
- While applying the brake pedal, measure the voltage between the inoperative stoplamp, harness side and ground as follows:
- Is the voltage greater than 10 volts?
Yes
REPAIR circuit 57 (BK) for an open. TEST the system for normal operation.
No
GO to I10.
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I10 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) (LH stoplamp) or circuit 5 (OG/LB) (RH stoplamp) for an open as necessary. TEST the system for normal operation.
No
INSTALL a new multifunction switch. TEST the system for normal operation.
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