Circuit Description
The body control module (BCM) supplies a reference voltage to the instrument panel dimmer switch through the instrument panel (I/P) lamps dimmer control circuit. The dimmer switch varies the voltage and returns the new voltage to the BCM through the low reference circuit. The BCM uses this voltage to determine the illumination level of the I/P lamps.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC B2622 Display Dimming Pulse Width Modulation (PWM) Input Circuit Low
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 I/P lamps dimmer control circuit is shorted to ground. |
| • | The low reference circuit is shorted to ground. |
Action Taken When the DTC Sets
The illumination of the I/P lamps defaults at full intensity.
Conditions for Clearing the DTC
| • | The BCM receives the clear code command from the scan tool. |
| • | A current DTC will clear when the conditions for setting the DTC are no longer present. |
| • | A history DTC clears after 100 malfunction free ignition cycles. |
Diagnostic Aids
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.
-
The normal operating voltage of the I/P dimmer switch is 0.4-4.5 volts.
-
This step determines if there is a problem with the dimmer switch.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Interior Lights Dimming Schematics | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Does the scan tool indicate that the I/P Dimmer Input parameter is within the specified range? | 0.4-4.5 V | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |
Does the scan tool indicate that the I/P Dimmer Input Data parameter is greater than the specified value? | 4.5 V | Go to Step 5 | Go to Step 4 | |
4 | Test the low reference circuit and the I/P lamps dimmer control circuit for short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 6 |
5 | Inspect for poor connections at the harness connector of the I/P 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 9 | Go to Step 7 |
6 | Inspect for poor connections at the harness connector of the body control module (BCM). 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 9 | Go to Step 8 |
7 | Replace the I/P dimmer switch. Refer to Instrument Panel Lamp Dimmer Switch Replacement . Did you complete the replacement? | -- | Go to Step 9 | Go to Step 9 |
8 | Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 9 | -- |
9 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
