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 B2585: Park Lamp Control Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Park Lamp Relay B+ | 1 | 1 | -- | --
Park Lamp Switch Signal | 2 | 2 | 2 | --
Park Lamp Relay Control | 1 | 1 | B2585 00 | --
Park Lamp Control | 1 | 1 | 1 | --
Park Lamp Ground | -- | 1 | -- | --
Park Lamp Switch Low Reference | -- | 2 | -- | --
1. Park Lamps Malfunction 2. Park Lamp Switch Malfunction

### Circuit/System Description

Battery positive voltage is applied at all times to both the coil and switch sides of the PRK/LAMP relay located in the underhood fuse block. The turn signal/multifunction switch is supplied with ground at G106 at all times. When the headlamp and panel dimmer switch is placed in either the HEAD or PARK position, ground is applied to the park lamp signal circuit to the body control module (BCM). The BCM responds by applying ground to the park lamp relay control circuit. This energizes the park lamp relay coil causing the relay switch contacts to close allowing battery voltage to flow through the FRT PRK LAMP and REAR PRK LAMP fuses to all of the park, tail, license, and marker lamps.

### Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

### Conditions for Setting the DTC

The park lamp relay control circuit is shorted to voltage.

### Action Taken When the DTC Sets

The park lamps will be inoperative from the headlamp and panel dimmer switch.

### Conditions for Clearing the DTC

• | This DTC will clear on current status after the condition for setting the fault is corrected.

• | A history DTC will clear after 100 consecutive ignition cycles without a fault present.

### Reference Information

#### Schematic Reference

Exterior Lights Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Exterior 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

#### Park Lamp Malfunction

1. Ignition OFF, disconnect the park lamp relay.
2. Connect a test lamp between the relay coil control circuit terminal 86 and B+.
3. Ignition ON, command the Park Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF..

⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.

⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

4. If all circuits test normal, test or replace the relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Relay Replacement

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