B2603
DTC B2602 or B2603
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 Descriptors
DTC B2602 00
- Daytime Running Lamp Control Circuit Low or Open
DTC B2603 00
- Daytime Running Lamp Control Circuit High
Diagnostic Fault Information
Circuit/System Description
The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary depending on outside lighting conditions. The body control module (BCM) provides a low reference ground to the ambient light sensor. The body control module monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lights (DRL) or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In daylight conditions the BCM will command the DRLs ON. During low light conditions the BCM will command the low beam headlamps ON. Any function or condition that turns on the headlamps will cancel DRL operation.
Conditions for Running the DTC
* The ignition switch is in the RUN position.
* The headlamp switch is in the AUTO position.
* The park brake is not applied.
* The gear selector is not in the PARK position.
Conditions for Setting the DTC
One of the following conditions must occur:
* The DRL relay control circuit is open, shorted to ground, or shorted to voltage.
* The DRL relay coil is open.
* The battery positive voltage to the DRL relay is open.
Action Taken When the DTC Sets
* The BCM stores DTC B2602 or B2603 in memory.
* The BCM disables the DRL relay control as long as the fault is present.
* The BCM disables the DRL relay control until the next key cycle after the fault is corrected.
Conditions for Clearing the DTC
* This DTC will clear on current status after the condition for setting the fault is corrected and the ignition is cycled.
* A history DTC will clear after 100 consecutive ignition cycles without a fault present.
Diagnostic Aids
* The park brake must not be set and the transmission must be is gear for the DRL to operate property.
* An open, short to ground, or a short to voltage in the following location may cause a malfunction to occur:
- The control circuit of the DRL relay coil
- The DRL relay
- The BCM
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics (Headlights/Daytime Running Lights (DRL) Schematics)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
Ignition ON, carefully supply sufficient light to the ambient light sensor to activate DRL mode. The BCM Output Data List should indicate that the DRL Status is On. The low beam headlamps should illuminate at a reduced intensity.
Circuit/System Testing
1. Ignition OFF, disconnect the DRL 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 B+ circuit 30 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, and the B+ circuit fuse is open, test the control circuit 87 for short to ground. If the circuit tests normal replace the DRL relay.
4. Connect a test lamp between B+ circuit terminal 85 and control circuit terminal 86.
5. Ignition ON, command the Daytime Running 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 short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM
6. If all circuits test normal, test or replace the DRL 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))
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming