Pinpoint Tests AW: DTC U0121

Instrumentation, Message Center and Warning Chimes

Pinpoint Tests

Pinpoint Test AW: DTC U0121

Normal Operation
- DTC U0121 (Lost Communication With Anti-Lock Brake System [ABS] Control Module) - sets in continuous memory in the Instrument Cluster (IC) if the 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 Information Bus.

This pinpoint test is intended to diagnose the following:

- ABS module
- IC



PINPOINT TEST AW: DTC U0121

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AW1 VERIFY THE CUSTOMER CONCERN


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

Yes
GO to AW2.

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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AW2 CHECK THE COMMUNICATION NETWORK


- Ignition ON.
- 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 AW3.

No
REFER to Information Bus.

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AW3 RETRIEVE THE RECORDED DTCs FROM THE IC SELF-TEST


- Check for recorded IC DTCs from the self-test.
- Is DTC B1317 or B1318 recorded?

Yes
Go To Pinpoint Test AP (B1317) or Go To Pinpoint Test AQ (B1318). Pinpoint Tests AP: DTC B1317 Pinpoint Tests AQ: DTC B1318

No
GO to AW4.

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AW4 RECHECK THE IC DTCs


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.

- Clear the DTCs. Repeat the IC self-test.
- Is DTC U0121 still present?

Yes
INSTALL a new ABS module. CLEAR the DTCs. REPEAT the IC self-test.

If DTC U0121 is still present, INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). 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.

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