B2418

DTC B2418 Daytime Running Lamps (DRL) Control Module Circuit Shorted To Voltage:

DTC B2418 Daytime Running Lamps (DRL) Control Module Circuit Shorted To Voltage (Part 1 Of 2):

DTC B2418 Daytime Running Lamps (DRL) Control Module Circuit Shorted To Voltage (Part 2 Of 2):

CIRCUIT DESCRIPTION
The Body Control Module (BCM) interfaces with the DRL control module through circuit 1970 to determine the ambient light operation mode. The BCM communicates this information to the Instrument Panel Cluster (IPC) through the Class II serial data link. Circuit 1970 also allows the BCM to turn on the headlamps for the twilight sentinel feature.

The BCM enters the twilight sentinel mode (turning on the headlamps by grounding circuit 1970) if the ignition is turned to the LOCK or OFF position when these conditions are met:
^ The headlamps switch is in the off position.
^ The headlamps are on due to night mode of the auto headlamp control.

CONDITIONS FOR SETTING THE DTC
The BCM detects a short to B+ in circuit 1970 ONLY when the twilight sentinel mode is active.

ACTION TAKEN WHEN THE DTC SETS
^ The BCM stores DTC B2418 in memory.
^ The BCM turns off its output to the DRL module.

CONDITIONS FOR CLEARING THE DTC
^ When the ignition switch is turned from the LOCK or OFF position to the RUN position, a current DTC B2418 is always cleared. If the short to B+ in circuit 1970 is still present when the BCM attempts to ground circuit 1970 to enter the twilight sentinel mode, DTC B2418 will NOT reset as a current DTC.
^ A history DTC will clear after 100 consecutive ignition cycles if the condition for the fault is no longer present.
^ Using a scan tool.

DIAGNOSTIC AIDS
^ The BCM sets DTC B2418 as a current DTC only if the short to B+ occurs while the BCM is in the twilight sentinel mode.
^ Check fuses for a possible open fuse, indicating that the circuit(s) protected by such fuse is contacting circuit 1970.
^ The following conditions may cause an intermittent malfunction to occur:
- An intermittent short to B+ in circuit 1970.
- The BCM is shorted to B+ internally.
- The DRL module is shorted to voltage internally.
^ If the DTC is a history DTC, the problem may be intermittent. Try performing the tests shown while wiggling wiring and connectors, this can often cause the malfunction to reappear.
^ DTC P1626 will set in the Powertrain Control Module (PCM) when the ignition switch is in the RUN position with the BCM disconnected. When BCM diagnostics and repairs are completed, refer to the Engine Controls for additional information on PCM related DTCs. Powertrain Management

TEST DESCRIPTION
Numbers below refer to the step numbers on the diagnostic table.
2. Checks for a short to B+ in circuit 1970.
3. Determines whether circuit 1970 has a short to B+ or the BCM is faulty.
4. Determines whether the malfunction is intermittent or the BCM is faulty.