Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC B2622: Display Dimming Pulse Width Modulation (PWM) Input Circuit LowDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
I/P Lamps Dimmer Control Circuit | B2622 | B2622 | -- | -- |
I/P Low Reference Circuit | B2622 | B2622 | -- | -- |
Dimmer Switch | B2622 | B2622 | -- | -- |
BCM | B2622 | B2622 | -- | -- |
Circuit/System 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.
Conditions for Running the DTC
The park lamp input to the BCM is active, park or headlamps ON.
Conditions for Setting the 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 to full intensity.
Conditions for Clearing the DTC
| • | A current DTC B2622 clears when the BCM no longer detects a short to battery positive voltage in the control circuit on the park lamp relay. |
| • | 100 consecutive ignition cycles have been recorded without the DTC being detected. |
| • | Using a scan tool can clear the DTC. |
Diagnostic Aids
The BCM monitors the voltage from the dimmer switch to determine the amount of intensity of the I/P back lighting.
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics
Connector End View Reference
Lighting Systems Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
Ignition ON, observe the scan tool I/P dimmer input. The reading should be between 0.0 and 4.5 volts and change with the operation of the dimmer switch.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the dimmer switch.
- Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit and ground.
- Ignition ON, verify the scan tool I/P dimmer input is greater than 4.5 volts.
- Install a 3-amp fused jumper wire between the signal circuit and the low reference circuit. Verify the scan tool I/P dimmer input is less than .5 volts.
- If all circuits test normal, test or replace the dimmer switch.
| ⇒ | If greater than 1.0 ohm, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
| ⇒ | If less than 4.5 volts, test the signal circuit for a short to ground. If the circuit tests normal, replace the BCM. |
| ⇒ | If greater than .5 volts, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM. |
Component Testing
- Ignition OFF, disconnect the harness connector at the dimmer switch.
- Test for 20 ohms to 10.0 K ohms of resistance between the signal terminal and the ground terminal.
| ⇒ | If the resistance is not within the specified range, replace the dimmer switch. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, programming, and setup |
