For 1990-2009 cars

### 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 B3600 03: Passenger Compartment Dimming Request Signal Circuit Voltage Below Threshold

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
I/P Dimmer Switch B+ Voltage Reference | -- | 1 | -- | --
I/P Dimmer Switch Signal | B1395 03, B3600 03 | B2652 00, B3600 03 | B1395 07 | --
I/P Dimmer Switch Ground | -- | 1 | -- | --
1. Interior Backlighting Malfunction

### Circuit/System Description

The instrument panel (I/P) lamp dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The I/P dimmer switch provides a voltage signal that will increase as the brightness of the lights are increased and decrease as the brightness of the lights are decreased. The body control module (BCM) provides a low reference signal and a B+ voltage reference to the I/P dimmer switch. When the I/P dimmer switch is placed in the desired position, the dimmed voltage setting is applied from the I/P dimmer switch through the I/P dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies the dimmed voltage to the I/P lamps supply voltage circuit and the interior backlighting components dim to the requested level. Ground for the I/P dimmer switch is provided at G201.

### Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

### Conditions for Setting the DTC

DTC B3600 03 will set when the BCM detects a short to ground or an open/high resistance in the I/P dimmer switch signal circuit.

### Actions Taken When the DTC Sets

• | The I/P dimmer switch will not operate.

• | The I/P dimming lamps will not illuminate.

### Conditions for Clearing the DTC

• | The condition responsible for setting the DTC no longer exists.

• | A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

### Reference Information

#### Schematic Reference

Interior Lights Dimming Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Interior Lighting Systems Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Testing

1. With a scan tool clear the DTC.
2. Ignition OFF, disconnect the harness connector at the I/P Dimmer switch.
3. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal C.

⇒ | If the test lamp does not illuminate, test the ground circuit for an open/high resistance.

4. Ignition ON, test for B+ between the voltage reference circuit terminal D and ground.

⇒ | If less than the specified value, test the voltage reference circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the BCM.

5. Verify the scan tool Dimming Control Signal parameter is less than 0.2 volts.

⇒ | If greater than the specified range, test the signal circuit terminal B for a short to voltage. If the circuit tests normal, replace the BCM.

6. Install a 3A fused jumper wire between the signal circuit terminal B and the voltage reference circuit terminal D. Verify the scan tool Dimming Control Signal parameter is greater than 2.5 volts.

⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

7. If all circuits test normal, test or replace the I/P dimmer switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Instrument Panel Lamp Dimmer Switch Replacement

• | Control Module References for BCM replacement, setup, and programming