Pinpoint Tests AO: DTC U0121
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test AO: DTC U0121
Normal Operation
- DTC U0121 (Lost Communication With Anti-Lock Brake System (ABS) Control Module) - sets in continuous memory DTC if data messages received from the ABS module over the High Speed Controller Area Network (HS-CAN) are missing for greater than 5 seconds.
This pinpoint test is intended to diagnose the following:
- ABS module
- Instrument Cluster (IC)
PINPOINT TEST AO: DTC U0121
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AO1 VERIFY THE CUSTOMER CONCERN
- Ignition ON.
- Verify that 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 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 Information Bus.
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AO3 RETRIEVE THE RECORDED DTCs FROM THE IC SELF-TEST
- Check for recorded IC DTCs from the self-test.
- Is DTC B1317 or B1318 recorded?
Yes
Go To Pinpoint Test AK (B1317) or Go To Pinpoint Test AL (B1318). Pinpoint Tests AK: DTC B1317 Pinpoint Tests AL: DTC B1318
No
GO to AO4.
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AO4 RECHECK THE IC DTCs
- Clear the DTCs. Repeat the IC self-test.
- Is DTC U0121 still present?
Yes
INSTALL a new ABS module. CLEAR the DTCs. REPEAT the IC self-test.
If DTC U0121 is still present, INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). 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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