Pinpoint Test AI: DTC U0121:00

Adaptive Headlighting

Pinpoint Tests

Pinpoint Test AI: DTC U0121:00

Normal Operation
- U0121:00 (Lost Communication With Anti-Lock Brake System (ABS) Control Module: No Sub Type Information) - sets by the Headlamp Control Module (HCM) if data messages (steering wheel angle) received from the ABS module over the High Speed Controller Area Network (HS-CAN) are missing for greater than 5 seconds. For a complete list of all network messages, refer to Information Bus.

This pinpoint test is intended to diagnose the following:

- HCM
- ABS module



PINPOINT TEST AI: DTC U0121:00

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AI1 VERIFY THE CUSTOMER CONCERN


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

Yes
GO to AI2.

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

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AI2 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 AI3.

No
REFER to Information Bus.

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AI3 RECHECK THE HCM DTCs


NOTE: If a new ABS module was 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.

- Clear the DTCs. Repeat the HCM self-test.
- Is DTC U0121:00 still present?

Yes
GO to AI4.

No
REFER to Information Bus.

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AI4 CHECK FOR DTC U0121:00 SET IN OTHER MODULES


- Clear all DTCs.
- Ignition OFF.
- Ignition ON.
- Wait 10 seconds.
- Enter the following diagnostic mode on the scan tool: Self-Test.
- Retrieve the continuous memory DTCs from all modules.
- Is DTC U0121:00 set in the Instrument Panel Cluster (IPC)?

Yes
INSTALL a new ABS module. REFER to Antilock Brakes / Traction Control Systems. CLEAR the DTCs. REPEAT the self-test.

No
INSTALL a new HCM. REFER to Headlamp Control Module (HCM) Headlamp Control Module (HCM). CLEAR the DTCs. REPEAT the self-test.

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