Pinpoint Test AR: DTC U0121:87

Instrumentation, Message Center and Warning Chimes

Pinpoint Tests

Pinpoint Test AR: DTC U0121:87

Normal Operation
- DTC U0121:87 (Lost Communication With Anti-Lock Brake System [ABS] Control Module: Missing Message) - sets 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 more than 5 seconds. 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 AR: DTC U0121:87

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AR1 VERIFY THE CUSTOMER CONCERN


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

Yes
GO to AR2.

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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AR2 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 AR3.

No
REFER to Module Communications Network Testing and Inspection.

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AR3 RETRIEVE THE RECORDED DTCs FROM THE IPC AND ABS MODULE SELF-TESTS


- Check for recorded DTCs from the IPC and ABS module self-tests.
- Is DTC U3003:16 or DTC U3003:17 recorded in the IPC or DTC B1317 or B1318 recorded in the ABS module?

Yes
For the IPC, GO to Pinpoint Test AY (U3003:16) or GO to Pinpoint Test AZ (U3003:17). For the ABS module, REFER to Vehicle Dynamic Systems Initial Inspection and Diagnostic Overview. Pinpoint Test AY: DTC U3003:16 Pinpoint Test AZ: DTC U3003:17

No
GO to AR4.

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AR4 RECHECK THE IPC DTCs


- Clear the DTCs. Repeat the IPC 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 IPC self-test.

If DTC U0121:87 is still present, INSTALL a new IPC. REFER to Instrument Panel Cluster (IPC) 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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