Pinpoint Test H: DTC U0121

WARNING: This page is about a different car, the 2013 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

H1 VERIFY THE CUSTOMER CONCERN
- Ignition ON.
- Allow at least 10 seconds for all modules to wake up and prove out.
- 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
- Using a scan tool, 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 ANY DTCs FROM THE TBC MODULE
- Enter the following diagnostic mode on the scan tool: Self Test - TBC Module.
- Is DTC U3003:16 (or B1318) or DTC U3003:17 (or B1317) recorded?
- Yes : For DTC B1317, GO to PINPOINT TEST D .
  For DTC B1318, GO to PINPOINT TEST E .
  
  For the ABS module, REFER to ANTI-LOCK BRAKE SYSTEM (ABS) & STABILITY CONTROL .
- No : GO to H4.
H4 CHECK FOR DTC U0121:00 SET IN OTHER MODULES
- Clear the DTCs.
- Ignition OFF.
- Wait at least 5 seconds to allow the TBC module to sleep (power down).
- Ignition ON.
- Allow at least 10 seconds for all modules to wake up and prove out.
- Using a scan tool, retrieve the continuous memory DTCs from the following modules:
  - Body Control Module (BCM)
  - Instrument Panel Cluster (IPC)
  - Power Steering Control Module (PSCM) (if equipped)
  - Transfer Case Control Module (TCCM) (if equipped)
- Is DTC U0121:00 set in any of these modules?
- 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.