Pinpoint Test J: One Or More Stoplamps Are Inoperative
Stoplamps
Pinpoint Tests
Pinpoint Test J: 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
The Central Junction Box (CJB) fuse 142 (15A) supplies voltage to the stoplamp switch when the ignition is ON. When the brake pedal is applied, the stoplamp switch routes voltage to the stoplamps.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Stoplamp switch
- Rear lamp jumper harness
- High mounted stoplamp
PINPOINT TEST J: 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.
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J1 DETERMINE THE INOPERATIVE STOPLAMP
- Ignition ON.
- Apply the brake pedal and observe the stoplamps.
- Are all the stoplamps inoperative?
Yes
VERIFY the CJB fuse 142 (15A) is OK. If OK, GO to J2. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. Diagrams By Number
No
If the high mounted stoplamp is inoperative, GO to J4. If a rear stoplamp is inoperative, GO to J6.
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J2 CHECK FOR VOLTAGE TO THE STOPLAMP SWITCH
- Disconnect: Stoplamp Switch C278.
- Measure the voltage between the stoplamp switch C278-1, circuit 15-LG23 (GN/WH), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to J3.
No
REPAIR circuit 15-LG23 (GN/WH) for an open. TEST the system for normal operation.
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J3 BYPASS THE STOPLAMP SWITCH
- Connect a fused jumper wire between the stoplamp switch C278-1, circuit 15-LG23 (GN/WH), harness side and the stoplamp switch C278-4, circuit 15S-LG23 (GN/WH), harness side.
- Do the stoplamps illuminate?
Yes
REMOVE the jumper wire. INSTALL a new stoplamp switch. REFER to Stoplamp Switch Service and Repair. TEST the system for normal operation.
No
REMOVE the jumper wire. REPAIR stoplamp switch output circuit for an open. TEST the system for normal operation.
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J4 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 15S-LG6 (GN/YE), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to J5.
No
REPAIR circuit 15S-LG6 (GN/YE) for an open. TEST the system for normal operation.
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J5 CHECK FOR VOLTAGE TO THE HIGH MOUNTED STOPLAMP USING THE CONNECTOR GROUND
- While applying the brake pedal, measure the voltage between the high mounted stoplamp C904-1, circuit 15S-LG6 (GN/YE), harness side and the high mounted stoplamp C904-2, circuit 31-LG6 (BK), harness side.
- Is the voltage greater than 10 volts?
Yes
INSTALL a new high mounted stoplamp. REFER to High Mounted Stoplamp Service and Repair. TEST the system for normal operation.
No
REPAIR circuit 31-LG6 (BK) for an open. TEST the system for normal operation.
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J6 CHECK FOR VOLTAGE TO THE REAR LAMP
- Disconnect: Inoperative Rear Lamp.
- While applying the brake pedal, measure the voltage between the LH rear lamp C414-6, circuit 15S-LG14 (GN/RD), harness side and ground; or between the RH rear lamp C417-6, circuit 15S-LG21 (GN/BK), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to J7.
No
REPAIR circuit 15S-LG14 (GN/RD) (LH rear lamp) or circuit 15S-LG21 (GN/BK) (RH rear lamp) for an open. TEST the system for normal operation.
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J7 CHECK FOR VOLTAGE TO THE REAR LAMP USING THE CONNECTOR GROUND
- While applying the brake pedal, measure the voltage between the LH rear lamp C414-6, circuit 15S-LG14 (GN/RD), harness side and the LH rear lamp C414-5, circuit 31-LF23 (BK), harness side; or between the RH rear lamp C417-6, circuit 15S-LG21 (GN/BK), harness side and the RH rear lamp C417-5, circuit 31-LF24 (BK), harness side.
- Is the voltage greater than 10 volts?
Yes
REPAIR or INSTALL a new rear lamp jumper harness. TEST the system for normal operation.
No
REPAIR circuit 31-LF23 (BK) (LH rear lamp) or circuit 31-LF24 (BK) (RH rear lamp) for an open. TEST the system for normal operation.
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