Pinpoint Test E: Lost Communication With Abs (Anti-Lock Brake System) Module U0121:87
- Refer to MODULE COMMUNICATIONS NETWORK
for schematic and connector information.
Normal Operation and Fault Conditions
REFER to: COMMUNICATIONS NETWORK .
DTC Fault Trigger Conditions
DTC Description Fault Trigger Condition BCM U0121:87 Lost Communication With Anti-Lock Brake System (ABS) Control Module "A": Missing Message A continuous memory DTC that sets in the BCM if messages from the ABS module through the GWM are missing. Possible Sources
- Communication network concern
- Battery voltage concern
- GWM
- ABS module
- BCM
NOTE: If new modules were installed prior to the DTC being set, the module configuration may be incorrectly set during the PMI or the PMI may not have been carried out. - E1 CHECK THE COMMUNICATION NETWORK
- Perform a network test.
Does the ABS module pass the network test?
Yes GO to E2 No DIAGNOSE no communication with the ABS module. REFER to: COMMUNICATIONS NETWORK . - E2 RETRIEVE THE DIAGNOSTIC TROUBLE CODES (DTCS) FROM THE BCM (BODY CONTROL MODULE) SELF-TEST
- Perform the BCM self-test.
Is DTC U3006:16 or U3006:17 recorded?
Yes For DTC U3006:16, GO to Pinpoint Test O For DTC U3006:17, GO to Pinpoint Test P No GO to E3 - E3 RETRIEVE THE DIAGNOSTIC TROUBLE CODES (DTCS) FROM THE ABS (ANTI-LOCK BRAKE SYSTEM) MODULE SELF-TEST
- Perform the ABS module self-test.
Are any voltage system related Diagnostic Trouble Codes (DTCs) recorded?
Yes REFER to: Anti-Lock Brake System (ABS) . No GO to E4 - E4 RECHECK THE BCM (BODY CONTROL MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)NOTE: If new modules were installed prior to the DTC being set, the module configuration may be incorrectly set during the PMI or the PMI may not have been carried out.
- Clear the Diagnostic Trouble Codes (DTCs).
- Ignition OFF.
- Ignition ON.
- Wait 10 seconds.
- Perform the BCM self-test.
Is DTC U0121:87 present?
Yes GO to E5 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. - E5 CHECK FOR DIAGNOSTIC TROUBLE CODES (DTCS) U0121:87 SET IN OTHER MODULES
- Clear all Diagnostic Trouble Codes (DTCs).
- Ignition OFF.
- Ignition ON.
- Wait 10 seconds.
- Retrieve all Continuous Memory Diagnostic Trouble Codes (CMDTCs).
Is DTC U0121:87 set in other modules?
Yes GO to E6 No GO to E7 - E6 CHECK FOR CORRECT ABS (ANTI-LOCK BRAKE SYSTEM) MODULE OPERATION
- Ignition OFF.
- Disconnect and inspect the ABS module connectors.
- Repair:
- corrosion (install new connector or terminals - clean module pins)
- damaged or bent pins - install new terminals/pins
- pushed-out pins - install new pins as necessary
- Reconnect the ABS module connectors. Make sure it seats and latches correctly.
- Operate the system and determine if the concern is still present.
Is the concern still present?
Yes CHECK OASIS for any applicable service articles: TSB, GSB, SSM or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new ABS. Refer to ANTI-LOCK BRAKE SYSTEM (ABS) MODULE . No The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues. - E7 CHECK FOR CORRECT BCM (BODY CONTROL MODULE) OPERATION
- Ignition OFF.
- Disconnect and inspect all BCM connectors.
- Repair:
- corrosion (install new connector or terminals - clean module pins)
- damaged or bent pins - install new terminals/pins
- pushed-out pins - install new pins as necessary
- Reconnect the BCM connectors. Make sure they seat and latch correctly.
- Operate the system and determine if the concern is still present.
Is the concern still present?
Yes CHECK OASIS for any applicable service articles: TSB, GSB, SSM or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new BCM. Refer to Body Control Module (BCM) . No The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.