GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2007 🢒 Lucerne 🢒 DTC 🢒 DTC B2585

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 B2585 00: Park Lamp Control Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Park Lamp Relay Control

2

1

B2585 00

--

  1. Park Lamps Inoperative
  2. Park Lamps Always On

Circuit/System Description

Battery voltage is applied at all times to both the coil and switch sides of the PRK LAMP Relay. When the headlamp switch is placed in the PARK position, ground is applied through the park lamp switch signal circuit to the body control module (BCM) . The BCM then applies a ground to the park lamp relay control circuit. This energizes the relay and applies voltage through both park lamp fuses and to all the park lamps.

Conditions for Running the DTC

The park lamps must be commanded on by the BCM.

Conditions for Setting the DTC

The BCM detects a short to voltage on the park lamp relay control circuit while trying to apply a ground to the circuit.

Action Taken When the DTC Sets

The BCM will deactivate the park lamp relay for the remainder of the ignition cycle.

Conditions for Clearing the DTC
    • The condition responsible for setting the DTC no longer exists.
    • A history DTC will clear once 100 consecutive malfunction ignition cycles have occurred.

Reference Information

Schematic Reference

Exterior Lights 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 Testing
  1. Ignition OFF, disconnect the park lamp relay.
  2. Connect a test lamp between B+ and the control circuit terminal 101.
  3. Ignition ON, command the Parking Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between commanded states.
    4. ⇒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 the circuit tests normal, replace the park lamp relay.

Component Test

Relay Test

  1. Ignition OFF, disconnect the park lamp relay.
  2. Test for 70-100 ohms of resistance between terminals 85 and 86.
    3. ⇒If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals:
    4. • 30 and 85
    • 30 and 86
    • 30 and 87
    • 85 and 87
    ⇒If not the specified value, replace the relay.
  4. Install a 10A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.
    5. ⇒If greater than the specified range, replace the relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement
    •  Control Module References for BCM replacement, setup, and programming