B2585
DTC B2585
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC B2585 00
- Park Lamp Control Circuit
Diagnostic Fault Information
Circuit/System Description
Battery positive voltage is applied at all times to both the coil and switch sides of the PARK LAMP Relay located in the underhood fuse block. When the headlamp 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 B+ to flow through the LT PRK fuse, RT PRK fuse, and the TRLR PRK fuse, to all of the park, tail, license, and marker lamps.
Conditions for Running the DTC
* Battery voltage must be between 9-16 V.
* Park lamps ON.
Conditions for Setting the DTC
The BCM detects a short to voltage in the PARK LAMP Relay control circuit.
Actions Taken When the DTC Sets
The park lamps will not operate.
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
Exterior Lights Schematics Exterior Lights Schematics
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation
Exterior Lighting Systems Description and Operation Exterior Lighting Systems
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Testing
1. Ignition OFF, disconnect the park lamp relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
• If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
4. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
5. Disconnect the harness connector at the appropriate park lamp.
6. Test for less than 5 ohm between the ground circuit terminal listed below and ground:
* Park/Turn Signal Lamp - Terminal G
* Tail/Stop and Turn Signal Lamp - Terminal GRD
* License Lamp - Terminal B
* Rear Fender Clearance Lamp - Terminal B
* Side Marker Lamp - Terminal A
* Roof Clearance Lamp - Terminal A
* Tailgate Marker Lamp - Terminal B
• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
7. Connect the harness connector at the park lamp.
8. Connect a 15 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the park lamp is activated.
• If the park lamp does not activate and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the park lamp.
• If the park lamp does not activate and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the park lamp.
9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
10. Command the Parking Lamps ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• 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.
11. If all circuits test normal, replace the park lamp relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)
* Roof Clearance Center Lamp Replacement (U01) Roof Clearance Center Lamp Replacement (U01)
* Roof Clearance Outer Lamp Replacement (U01) Roof Clearance Outer Lamp Replacement (U01)
* Rear Fender Clearance Lamp Replacement Service and Repair
* Rear License Plate Lamp Replacement (Silverado GMC) Rear License Plate Lamp ReplacementRear License Plate Lamp Replacement (VF7) Rear License Plate Lamp Replacement
* Tail Lamp Replacement (Chevrolet) Service and RepairTail Lamp Replacement (GMC) Service and RepairTail Lamp Replacement (HD) Service and Repair
* Control Module References Control Module References for BCM replacement, setup, and programming