Pinpoint Test AE: DTC U0121:87

Adaptive Headlighting

Pinpoint Test AE: DTC U0121:87

Normal Operation
- DTC U0121:87 (Lost Communication With Anti-Lock Brake System (ABS) Control Module: Missing Message) - sets continuous by the Headlamp Control Module (HCM) if data messages received from the ABS module over the High Speed Controller Area Network (HS-CAN) are missing. For a complete list of all network messages, refer to Module Communications Network Testing and Inspection.

This pinpoint test is intended to diagnose the following:

- HCM
- ABS module


PINPOINT TEST AE: DTC U0121:87

NOTE: If new modules were installed prior to the DTC being set, the module configuration may be incorrectly set during the Programmable Module Installation (PMI) or the PMI may not have been carried out.

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AE1 VERIFY THE CUSTOMER CONCERN

- Ignition ON.
- Verify that there is an observable symptom present.
- Is an observable symptom present?

Yes
GO to AE2.

No
The system is operating normally at this time. The DTC may have been set due to high network traffic or an intermittent fault condition.

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AE2 CHECK THE COMMUNICATION NETWORK

- Enter the following diagnostic mode on the scan tool: Network Test.
- Carry out the network test.
- Does the ABS module pass the network test?

Yes
GO to AE3.

No
REFER to Module Communications Network Testing and Inspection.

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AE3 RETRIEVE THE RECORDED DTCs FROM THE HCM SELF-TEST

- Check for recorded DTCs from the HCM self-test.
- Is DTC U3003:16 or DTC U3003:17 recorded?

Yes
For DTC U3003:16, GO to Pinpoint Test AH. Pinpoint Test AH: DTC U3003:16

For DTC U3003:17 GO to Pinpoint Test AI. Pinpoint Test AI: DTC U3003:17

No
GO to AE4.

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AE4 RECHECK THE HCM DTCs

- Enter the following diagnostic mode on the scan tool: HCM Self-Test.
- Clear the DTCs. Repeat the HCM self-test.
- Is DTC U0121:87 still present?

Yes
INSTALL a new ABS module. REFER to Vehicle Dynamic Systems Service and Repair. CLEAR the DTCs. REPEAT the self-test.

If DTC U0121:87 is still present, INSTALL a new HCM. REFER to Headlamp Control Module (HCM) Service and Repair. TEST the system for normal operation.

No
The system is operating correctly at this time. The DTC may have been set due to high network traffic or an intermittent fault condition.

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