B257C

DTC B257C or B257D

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 B257C 00
- Left Headlamp Assembly Malfunction

DTC B257D 00
- Right Headlamp Assembly Malfunction

Diagnostic Fault Information





Circuit/System Description

When the headlight switch is placed in low beam position, the body control module (BCM) energizes the low beam headlamp relay which passes battery voltage to the respective headlamp voltage supply circuits. Each headlamp monitors this voltage and passes this information to the headlamp control module via the local interconnect network (LIN) communication bus.

Conditions for Running the DTC

The headlamps are turned ON.

Conditions for Setting the DTC

The headlamp control module detects a difference between the reported state of the headlamp from the headlamp and the reported state from the BCM.

Action Taken When the DTC Sets

The appropriate headlamp is inoperative.

Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists.

Diagnostic Aids

If both DTCs B257C and B257D are set, test the low beam relay for an open condition.

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 (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 (Programming and Relearning) for scan tool information

Circuit/System Verification

Ignition ON, command the headlamps ON and OFF with the headlamp switch.

The headlamps should turn ON and OFF.

Circuit/System Testing

1. Ignition OFF, disconnect the appropriate harness connector at the inoperative headlamps listed below:

* E13L Headlamp Assembly - Left
* E13R Headlamp Assembly - Right

2. Test for less than 5 ohm between the appropriate headlamp ground circuit harness connector terminal G and ground.

• If greater than the specified value, test the ground circuit for an open/high resistance.

3. Reconnect the headlamp connector and remove the appropriate fuse listed below:

* F50 UA Left Low Beam
* F49 UA Right Low Beam

4. Verify that the appropriate headlamp does not illuminate.

• If the headlamp does illuminate, test the fuse output circuit for a short to voltage.

5. Install a 10 A fused jumper wire between appropriate fuse output contact and B+. Verify that the appropriate low beam illuminates.

• If the headlamp does not illuminate, test the fuse output circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the appropriate bulb.

6. If all circuits test normal, replace the K26 Headlamp Control Module.

Component Testing

Relay Test
1. Ignition OFF, disconnect the KR49 Headlamp Low Beam Relay.
2. Test for 60-180 ohm between terminals 1 and 2.

• If the resistance is not within the specified range, replace the KR49 Headlamp Low Beam Relay.

3. Test for infinite resistance between the following terminals:

* 1 and 3
* 3 and 5
* 2 and 5
* 1 and 3

• If not the specified value, replace the KR49 Headlamp Low Beam Relay.

4. Install a 15 A fused jumper wire between relay terminal 1 and 12 V. Install a jumper wire between relay terminal 2 and ground. Test for less than 2 ohm between terminals 3 and 5.

• If greater than the specified range, replace the KR49 Headlamp Low Beam 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))
* Headlamp Replacement (Headlamp Replacement)
* Control Module References (Programming and Relearning) for headlamp control module replacement, setup, and programming