Pinpoint Test M : DTC (Diagnostic Trouble Code) U0121:87
WARNING: This page is about a different car, the 2018 Lincoln Navigator. However, it is still accessible from the selected car via links, so may be relevant.
- M1 VERIFY THE CUSTOMER CONCERN
- Ignition ON.
- Verify whether an observable symptom is present.
Is an observable symptom present?
Yes GO to M2 No CLEAR the DTC. The system is operating correctly at this time. The DTC may have been set due to high network traffic or an intermittent fault condition. - M2 CHECK THE COMMUNICATION NETWORK
- Using a diagnostic scan tool, perform the network test
Does the ABS module pass the network test?
Yes GO to M3 No REFER to: Communications Network . - M3 PERFORM THE ABS (ANTI-LOCK BRAKE SYSTEM) MODULE SELF-TEST
- Using a diagnostic scan tool, perform the ABS module self-test.
Are any non-network Diagnostic Trouble Codes (DTCs) present?
Yes DIAGNOSE all non-network Diagnostic Trouble Codes (DTCs). REFER to: Anti-Lock Brake System (ABS) and Stability Control . No GO to M4 - M4 PERFORM THE IPMB (IMAGE PROCESSING MODULE B) SELF-TEST
- Using a diagnostic scan tool, perform the IPMB self-test.
Are any non-network Diagnostic Trouble Codes (DTCs) present?
Yes DIAGNOSE all non-network Diagnostic Trouble Codes (DTCs). REFER to DTC Chart: IPMB . No GO to M5 - M5 RECHECK THE IPMB (IMAGE PROCESSING MODULE B) DIAGNOSTIC TROUBLE CODES (DTCS)
- Using a diagnostic scan tool, clear the IPMB Diagnostic Trouble Codes (DTCs).
- Ignition OFF.
- Ignition ON.
- Wait 10 seconds.
- Using a diagnostic scan tool, retrieve the IPMB Continuous Memory Diagnostic Trouble Codes (CMDTCs).
Is DTC U0121:87 still present?
Yes GO to M6 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. - M6 CHECK FOR OTHER CAUSES OF COMMUNICATION NETWORK CONCERN
- CHECK the vehicle service history for recent service actions related to the ABS module or IPMB if recent service history is found:
- verify correct replacement module was installed
- vehicle parts build may be used to verify correct part fitment
- verify the configuration of replacement module was correct
- re-configure module using as-built data if prior configuration is suspect
- verify the module was not obtained from a like vehicle and installed into customer vehicle
- return the swapped module to source vehicle and obtain new replacement module
- verify correct replacement module was installed
- Operate the system and determine if the observable symptom is still present.
Is the observable symptom still present?
Yes GO to M7 No The system is operating correctly at this time. The concern may have been due to incorrect parts replacement procedures or incorrect module configuration. - CHECK the vehicle service history for recent service actions related to the ABS module or IPMB if recent service history is found:
- M7 CHECK FOR CORRECT ABS (ANTI-LOCK BRAKE SYSTEM) MODULE OPERATION
- Ignition OFF.
- Disconnect and inspect all 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 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 ABS module. REFER to: Anti-Lock Brake System (ABS) Module . No The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.