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: Voltage Below Threshold
DTC B3600 07: Voltage Above Threshold

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
I/P Dimming Voltage Reference | B1395 03 | B1395 03 | B1395 07 | B1395 03, B1395 07
I/P Dimming Control Circuit | B3600 03 | B3600 03 | B3600 07 | B3600 03, B3600 07

### Circuit/System Description

Voltage for the interior backlighting components is supplied from the CHMSL/DIMR in the instrument panel I/P electrical center to the body control module (BCM). The BCM applies a voltage reference through the instrument panel (I/P) dimming voltage reference circuit to the interior lamp dimming switch, which is part of the headlamp switch. Which is part of the turn signal multi function switch. When the dimming switch is placed in the desired position, the dimmed voltage setting is applied from the interior lamp dimming switch through the I/P dimming control circuit to the BCM. The BCM then applies the dimmed voltage to the I/P lamps supply voltage circuit and they dim to the correct level. The I/P lamps are located in the following components:

• | Cigar lighter

• | Driver Information Center DIC switch

• | Door lock switches

• | Fog Lamp switch

• | Headlamp switch

• | Hazard switch

• | HVAC Control

• | I/P cluster

• | Power window switch

• | Power mirror switches

• | PRNDL

• | Radio

• | Rear Seat Audio if equipped

• | Rear HVAC Control if equipped

• | Steering Wheel Controls

• | Sunroof switch

• | Sunshade switch

• | TCS switch

• | Universal garage door opener switch

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

#### B3600 03

The BCM detects a voltage that is lower then 5 volts on the I/P dimming control circuit.

#### B3600 07

The BCM detects a voltage that is higher then 5 volts on the I/P dimming control circuit.

### Action Taken When the DTC Sets

The I/P lamps are not illuminated.

### Conditions for Clearing the DTC

The BCM clears this code from current when the fault is removed from the system.

### Reference Information

#### Schematic Reference

Interior Lights Dimming Schematics

#### Connector End View Reference

Lighting Systems Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Output Controls

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Verification

Ignition ON, cover the ambient light sensor, vary the interior lamp dimming switch from dim to full bright. The I/P lamps should dim and then become full bright.

### Circuit/System Testing

1. Clear the DTC. Disconnect the headlamp switch.
2. Connect a DMM between the I/P dimming voltage reference circuit and the negative terminal of the battery.
3. Ignition ON, test for 9-14 volts.

⇒ | If less then 9 volts, test the I/P dimming voltage reference circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the BCM.

⇒ | If greater than 14 volts, test the I/P dimming voltage reference circuit for a short to voltage. If the circuit/connections test normal, replace the BCM.

4. Disconnect the DMM. Install a jumper between I/P dimming voltage reference circuit and the I/P dimming control circuit.
5. Verify that DTC B3600 03 does not set.

⇒ | If the DTC resets, then test for a short to ground in the I/P dimming control circuit. If the circuit/connections test normal, replace the BCM.

6. If all circuits/connections test normal, replace the turn signal multi function switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Turn Signal Multifunction Switch Replacement

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