Pinpoint Test B: DTC U0121:00
Body Control Module (BCM)
Pinpoint Test B: DTC U0121:00
Normal Operation
- DTC U0121:00 (Lost Communication With Anti-Lock Brake System (ABS) Control Module: No Sub Type Information) - sets in the Body Control Module (BCM) if data messages received from the ABS module are missing. 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:
- Communication network concern
- ABS module
- BCM
PINPOINT TEST B: DTC U0121:00
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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 correctly at this time. The DTC may have been set due to high network traffic or an intermittent fault condition.
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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 Module Communications Network Testing and Inspection, The ABS Module Does Not Respond To The Scan Tool.
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B3 RETRIEVE THE RECORDED DTCs FROM THE BCM SELF-TEST
- Check for recorded BCM DTCs from the self-test.
- Is DTC U3003:16 or DTC U3003:17 recorded?
Yes
For DTC U3003:16, GO to Pinpoint Test F. For DTC U3003:17, GO to Pinpoint Test G. Pinpoint Test F: DTC U3003:16 Pinpoint Test G: DTC U3003:17
No
GO to B4.
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B4 CHECK FOR DTCs U3003:16 AND U3003:17 FROM THE ABS MODULE SELF-TEST
- Retrieve the continuous memory DTCs from the ABS module.
- Is DTC U3003:16 or DTC U3003:17 recorded?
Yes
REFER to Vehicle Dynamic Systems Testing and Inspection.
No
GO to B5.
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B5 RECHECK THE BCM 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 may not have been carried out.
- Clear the DTCs. Repeat the BCM self-test.
- Is DTC U0121:00 still present?
Yes
GO to B6.
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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B6 CHECK FOR DTC U0121:00 or U0121 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 U0121:00 or DTC U0121 set in any other module?
Yes
INSTALL a new ABS module. CLEAR the DTCs. REPEAT the BCM self-test.
No
INSTALL a new BCM. REFER to Body Control Module (BCM) Body Control Module (BCM). TEST the system for normal operation.
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