Circuit Description
The body control module (BCM) supplies voltage to the instrument panel dimmer switch through the instrument panel dimmer switch signal circuit. The dimmer switch varies the voltage and returns the new voltage to the BCM through the dimmer switch signal return circuit. The BCM uses this voltage to determine the illumination level of the instrument panel lamps.
Conditions for Running the DTC
The park lamp input to the BCM is active (park or headlamps on).
Conditions for Setting the DTC
Any of the following conditions will set this DTC:
| • | The dimmer switch signal is open for 5 seconds. |
| • | The dimmer switch signal return is open for 5 seconds. |
| • | The dimmer switch signal return is shorted to battery for 5 seconds. |
Action Taken When the DTC Sets
The illumination of the instrument panel lamps is forced to full intensity.
Conditions for Clearing the DTC
| • | The conditions for setting the DTC are no longer present. |
| • | A history DTC clears after 100 malfunction free ignition cycles. |
| • | The BCM receives the clear code command from the scan tool. |
Diagnostic Aids
| • | If the dimmer switch signal return becomes shorted to ground, no DTC will be set but the instrument panel lamps will be at full intensity. |
| • | If the DTC is a history DTC, the problem may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The normal operating voltage of the instrument panel dimmer switch is 0.5-11.5 volts.
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If the value is above 11.5 volts, with the sensor disconnected, an open or short to voltage exists. If the value is below 0.5 volts, a short to ground exists.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Interior Lights Dimming Schematics | ||||
1 | Did you perform the Lighting System Diagnostic System Check? | -- | Go to Step 2 | |
Does the scan tool indicate that the INTERIOR DIM POT parameter is within the specified range? | 0.5-11.5 volts | Go to Step 5 | Go to Step 3 | |
Does the scan tool indicate that the INTERIOR DIM POT data parameter is greater than the specified value? | 11.5 volts | Go to Step 5 | Go to Step 4 | |
4 | Test the signal circuit and the return circuit of the instrument panel dimmer switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6 |
5 | Test the signal circuit and the return circuit of the instrument panel dimmer switch for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 |
6 | Inspect for poor connections at the harness connector of the instrument panel dimmer switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 |
7 | Inspect for poor connections at the harness connector of the body control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 |
8 | Replace the instrument panel dimmer switch. Refer to Instrument Panel Lamp Dimmer Switch Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
9 |
Important: Perform the set up procedure for the body control module. Replace the body control module. Refer to Body Control Module Replacement in Body Control System . Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
