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 Descriptors

DTC B3600 03 : Dimmed Illumination Switch Circuit Low Voltage
DTC B3600 07 : Dimmed Illumination Switch Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
I/P Dimmer Switch Signal | B3600 03 | B3600 03 | B3600 07 | --
Headlamp Switch Low Reference | -- | 1 | -- | --
1. Headlamps Malfunction

### Circuit/System Description

The instrument panel (I/P) lamp dimmer switch is incorporated into the headlamp switch assembly. The I/P 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 instrument panel cluster (IPC) provides a low reference signal and a 12-volt 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 IPC. The IPC 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 the headlamp switch low reference circuit through the IPC.

### Conditions for Running the DTC

• | Battery voltage must be between 9-16 volts.

• | Park lamps ON.

### Conditions for Setting the DTC

#### B3600 03

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

#### B3600 07

The DTC will set when the IPC detects a short to voltage 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 headlamp switch.
3. Ignition OFF, verify a test lamp illuminates between B+ and the low reference circuit terminal 11.

⇒ | If the test lamp does not illuminate, test the ground circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the IPC.

4. Verify the scan tool Switch Illumination Dimming parameter displays DISABLED or INVALID.

⇒ | If not the specified value, test the signal circuit terminal 4 for a short to voltage. If the circuit tests normal, replace the IPC.

5. Install a 3A fused jumper wire between the signal circuit terminal 4 and the low reference circuit terminal 11. Verify the scan tool Switch Illumination Dimming parameter displays BRIGHT or DARK.

⇒ | If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the IPC.

6. 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.

• | Headlamp Switch Replacement

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