2010 Cadillac Truck SRX AWD V6-3.0L Page 297
Component Testing
Relay Test
1. Ignition OFF, disconnect the KR49 headlamp low beam relay.
2. Test for 60-180 ohm between terminals 85 and 86.
瀚慖f not within the specified range, replace the KR49 headlamp low beam relay.
3. Test for infinite resistance between the following terminals:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
瀚慖f not the specified value, replace the KR49 headlamp low beam relay.
4. Install a 15A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground. Test for
less than 2 ohm between terminals 30 and 87.
瀚慖f greater than the specified range, replace the KR49 headlamp low beam relay.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Headlamp Replacement (See: Lighting and Horns/Headlamp/Service and Repair/Removal and Replacement/Headlamp Replacement)
* Relay Replacement (Attached to Wire Harness) (See: Power and Ground Distribution/Power Distribution Relay/Service and Repair/Relay
Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (See: Power and Ground Distribution/Power
Distribution Relay/Service and Repair/Relay Replacement (Within an Electrical Center))
* Control Module References (See: Testing and Inspection/Programming and Relearning) for headlamp control module replacement, setup
and programming
B257D
DTC B257C or B257D
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/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
The headlamp control module calculates the headlamp angle and sends commands to the left and right adaptive forward lighting system headlamp
actuators. The headlamp actuators drive the headlamps to the position commanded by the headlamp control module. The headlamp control module
monitors the headlamp actuator motor control circuits for proper circuit continuity and for shorts to ground or voltage. If a malfunction is detected,
a DTC will be stored in memory and the driver will be notified with a message displayed over the driver information center located on the
