Pinpoint Test H: DTC U0121:00 Or DTC U1029

Cruise Control

Pinpoint Test H: DTC U0121:00 Or DTC U1029

Normal Operation

- DTC U0121:00 (Lost Communication With Anti-Lock Brake System (ABS) Control Module: No Sub-Type Information)- sets in the Cruise-Control Module (C-CM) if 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.

- DTC U0129 (Lost Communication With Brake System Control Module)- sets in the PCM if data messages received from the ABS module over the High Speed Controller Area Network (HS-CAN) are missing. The adaptive cruise control is deactivated if it does not receive an active braking message from the ABS module. For a complete list of all network messages, refer to Information Bus.

This pinpoint test is intended to diagnose the following:

- ABS module

- C-CM (Cruise-Control Module)

PINPOINT TEST H : DTC U0121:00 OR DTC U1029

H1 VERIFY THE CUSTOMER CONCERN

- Ignition ON.

- Verify that there is an observable symptom present.

Is an observable symptom present?

Yes
GO to H2.

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.

H2 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 H3.

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

H3 RETRIEVE THE RECORDED DTCs FROM THE C-CM (Cruise-Control Module) AND PCM SELF-TEST

- Check for recorded DTCs from the following modules.
- C-CM (Cruise-Control Module)

- ABS module

- PCM


Are any low or high voltage DTCs recorded?

Yes
For the C-CM (Cruise-Control Module), GO to Pinpoint Test Q (U3003:16) or GO to Pinpoint Test R (U3003:17). Pinpoint Test Q: DTC U3003:16 Pinpoint Test R: DTC U3003:17

For all others, REFER to the Diagnostic Trouble Code (DTC) Chart in Body Control Systems. Body Control Module / Body Control Systems

No
GO to H4.

H4 CHECK FOR DTC U0121:00 OR DTC U1029 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.

Does the C-CM (Cruise-Control Module) set DTC U0121:00 and the PCM set DTC U1029?

Yes
INSTALL a new ABS module.

No
If the C-CM (Cruise-Control Module) sets DTC U0121:00, INSTALL a new C-CM (Cruise-Control Module). REFER to Cruise-Control Module (C-CM) .

If the PCM sets DTC U1029, INSTALL a new PCM.