Pinpoint Tests AO: DTC U0121:00

Instrumentation, Message Center and Warning Chimes

Pinpoint Test AO: DTC U0121:00

Normal Operation
- DTC U0121:00 (Lost Communication With Anti-Lock Brake System (ABS) Control Module: No Sub Type Information) - sets in continuous memory in the Instrument Panel Cluster (IPC) if data messages received from the ABS module over the High Speed Controller Area Network (HS-CAN) are missing for 5 seconds or more. 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:

- ABS module
- IPC

PINPOINT TEST AO: DTC U0121:00

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AO1 VERIFY THE CUSTOMER CONCERN

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

Yes
GO to AO2.

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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AO2 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 AO3.

No
REFER to Module Communications Network Testing and Inspection.

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AO3 RETRIEVE THE RECORDED DTCs FROM THE ABS MODULE SELF-TEST

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

Yes
REFER to Vehicle Dynamic Systems Testing and Inspection.

No
GO to AO4.

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AO4 RETRIEVE THE RECORDED DTCs FROM THE IPC SELF-TEST

- Check for recorded DTCs from the IPC self-test.
- Is DTC U3006:16 or DTC U3006:17 recorded?

Yes
For DTC U3006:16, GO to Pinpoint Test AU. For DTC U3006:17, GO to Pinpoint Test AV. Pinpoint Tests AU: DTC U3006:16 Pinpoint Tests AV: DTC U3006:17

No
GO to AO5.

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AO5 RECHECK THE IPC 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.
- Wait 10 seconds.
- Repeat the IPC self-test.
- Is DTC U0121:00 still present?

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

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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