B2585

CIRCUIT DESCRIPTION
The PARK LPS 30 A fuse in the engine wiring harness junction block supplies battery positive voltage to both the park lamp relay switch contacts and the battery positive voltage circuit of the park lamp relay coil. The body control module (BCM) provides ground to the park lamp relay control circuit. When the park lamps are turned on the BCM energizes the park lamp relay. Current flow is from the park lamp relay to the FR PRK 10 A fuse, TRA PRK 15 A fuse, LR PRK 10 A fuse, and the RR PRK 10 A fuse, and to their respective park and marker lamps. The front park and marker lamps are grounded at G100. The rear park and license lamps are grounded at G401. The roof marker and clearance lamps are grounded at G200.

The CTSY LP 15 A fuse in the engine wiring harness junction block supplies battery positive voltage to both the inadvertent power relay switch contacts and the battery positive voltage circuit of the inadvertent power relay coil. The body control module (BCM) provides a ground or control circuit to the park lamp relay coil circuit. When the driver presses the cargo lamp switch, the BCM energizes the inadvertent power relay. Current flow is from the inadvertent power relay to the cargo lamps. The cargo lamps are grounded at G203.

The TRL L TURN 10 A fuse and TRL R TURN 10 A fuses in the engine wiring harness junction block supply battery positive voltage to separate park lamp circuits connected to the trailer wiring harness.

CONDITIONS FOR RUNNING THE DTC
^ The key is in the RUN position.
^ The park brake is released.
^ The headlamp and panel dimmer switch is in the AUTO mode.
^ The ambient light sensor is in the DARK state.
^ The system voltage must be between 9.0 and 16.0 volts.

CONDITIONS FOR SETTING THE DTC
^ The key is in the RUN position.
^ The park brake is released.
^ The headlamp and panel dimmer switch is in the AUTO mode.
^ The ambient light sensor is in the DARK state.
^ There is a short to ground in the interior park lamps supply voltage circuit or an open in the park lamp relay control circuit.
^ If the Interior park lamps supply voltage circuit is open, regardless of the headlamp and panel dimmer switch position, the DTC will set.
^ If the park lamp relay control circuit is open, with the headlamp and panel dimmer switch in the AUTO mode, the DTC will set.
^ The system voltage must be between 9.0 and 16.0 volts.
^ The above conditions must be met for 0.5 seconds.

ACTION TAKEN WHEN THE DTC SETS
The park lamps will be inoperative in the AUTO mode.

CONDITIONS FOR CLEARING THE DTC
^ A current DTC will clear immediately when the condition for setting the fault is corrected with the key ON.
^ A history DTC will clear after 100 consecutive ignition cycles without a fault present.
^ A clear codes message is sent by the scan tool.

DIAGNOSTIC AIDS

IMPORTANT: Use the appropriate probe from the J 35616-A connector test adapter kit for any probing of the electrical components mentioned in this table to avoid damage to the terminals.

Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent and Poor Connections in Diagnostic Aids.

TEST DESCRIPTION

Steps 1-13:

Steps 14-26:

The number(s) below refer to the step number(s) on the diagnostic table.
2. Command both the ON and OFF states. Repeat the commands as necessary.
3. This step determines if the condition is located in the interior lamps supply voltage circuit.
4. This step determines if the condition is located on the coil side or the switch side of the circuit.
6. This step determines if the body control module (BCM) is providing ground for the park lamp relay.
7. This step determines if a ground is constantly being applied to the park lamp relay.
25. After you replace the BCM, you must calibrate the new module for proper operation.