Pinpoint Test B: DTC U0121:87

Body Control Module (BCM)

Pinpoint Test B: DTC U0121:87

Normal Operation

- DTC U0121:87 (Lost Communication With Anti-Lock Brake System (ABS) Control Module: Missing Message)- sets in the BCM (Body Control Module) if data messages received from the ABS module are missing. For a complete list of all network messages, refer to Information Bus.

This pinpoint test is intended to diagnose the following:

- Communication network concern

- ABS module

- BCM (Body Control Module)

PINPOINT TEST B : DTC U0121:87

B1 VERIFY THE CUSTOMER CONCERN

- Ignition ON.

- Verify that there is an observable symptom present.

Is an observable symptom present?

Yes
GO to B2.

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.

B2 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 B3.

No
REFER to Information Bus, The ABS Module Does Not Respond To The Scan Tool.

B3 RETRIEVE THE RECORDED DTCs FROM THE BCM (Body Control Module) AND SELF-TEST

- Check for recorded BCM (Body Control Module) DTCs from the self-test.

Is DTC U3003:16 or DTC U3003:17 recorded?

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

For DTC U3003:17, GO to Pinpoint Test G. Pinpoint Test G: DTC U3003:17
No
GO to B4.

B4 RECHECK THE BCM (Body Control Module) DTCs

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

- Clear the DTCs. Repeat the BCM (Body Control Module) self-test.

Is DTC U0121:87 still present?

Yes
GO to B5.

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.

B5 CHECK FOR DTC U0121:87 SET IN OTHER MODULES

- Clear the 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 U0121:87 set in any other module?

Yes
INSTALL a new ABS module. CLEAR the DTCs. REPEAT the BCM (Body Control Module) self-test.

No
INSTALL a new BCM (Body Control Module). REFER to Body Control Module (BCM) . TEST the system for normal operation.