Pinpoint Test H: DTC U0121
WARNING: This page is about a different car, the 2013 Ford F-550 Super Duty, 2013 Ford F-450 Super Duty, 2013 Ford F-350 Super Duty, and 2013 Ford F-250 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
- 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 MODULE COMMUNICATIONS NETWORK to diagnose the ABS module does not respond to the scan tool.
- H3 RETRIEVE THE RECORDED DTCs FROM THE TBC AND ABS MODULE SELF-TESTS
- Check for recorded TBC and ABS module DTCs from the self-test.
- Is DTC U3003:16 (or B1318) or DTC U3003:17 (or B1317) recorded?
- Yes
: For the TBC module, REFER to DTC CHARTS .
For the ABS module, REFER to ANTI-LOCK BRAKE SYSTEM (ABS) & STABILITY CONTROL .
- No : GO to H4.
- H4 CHECK FOR DTC U0121:87 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 U0121:87 or DTC U0121 set in more than one module?
- Yes : INSTALL a new ABS module. REFER to ANTI-LOCK BRAKE SYSTEM (ABS) & STABILITY CONTROL . CLEAR the DTCs. REPEAT the ABS module self-test.
- No : INSTALL a new TBC module. REFER to TRAILER BRAKE CONTROL (TBC) MODULE . TEST the system for normal operation.