LEMON Manuals: Even more car manuals for everyone
Home >> Honda >> 2007 >> Fit Base, Standard >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 1 (Automatic Transmission) >> DTC Troubleshooting >> DTC U0121: Lost Communication with ABS Modulator-Control Unit

DTC U0121: Lost Communication with ABS Modulator-Control Unit

WARNING: This page is about a different variant/trim than selected.
NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review GENERAL TROUBLESHOOTING INFORMATION  .
  1. Clear the DTC with the HDS.
  2. Turn the ignition switch to ON (II).
  3. Check that DTC U0121 recurs.

    Is DTC U0121 indicated? 

    YES  - Go to step  4.

    NO  - Intermittent failure, the system is OK at this time.

  4. Check whether any DTC is indicated in the DTCs/ Freeze Data in ABS Mode Menu with the HDS.

    Is any DTC indicated in the ABS? 

    YES  - Troubleshoot the indicated DTC in the ABS system (see ABS INDICATOR ).

    NO  - Go to step  5.

  5. Turn the ignition switch to LOCK (0).
  6. Jump the SCS line with the HDS.
  7. Disconnect PCM connector E (31R).
  8. Disconnect the ABS modulator-control unit 25P connector.
  9. Check for continuity between PCM connector terminal E11 and ABS modulator-control unit 25P connector terminal No. 1, and between E24 and terminal No. 17.
    Fig 1: Checking Continuity Between PCM And ABS Modulator-Control Unit Connector Terminal And Between E24 And Terminal No. 17
    G05455283

    Is there continuity? 

    YES  - Go to step  10.

    NO  - Go to step  15.

  10. Reconnect all connectors.
  11. Update the A/T software in the PCM if it does not have the latest software (see UPDATING THE PCM ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ).
  12. Turn the ignition switch to ON (II).
  13. Check for DTC(s) in the DTCs/Freeze Data in A/T Mode Menu with the HDS.

    Is DTC U0121 indicated? 

    YES  - If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE PCM ), then recheck. If the PCM was substituted, go to step  1.

    NO  - Go to step  14.

  14. Monitor the OBD status for U0121 in the DTCs/ Freeze Data in A/T Mode Menu for a pass/fail.

    Does the HDS indicate PASSED? 

    YES  - If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM (see ECM/PCM REPLACEMENT ). If any other DTCs were indicated on step 13, go to the indicated DTC's troubleshooting.

    NO  - Check for poor connections and loose terminals at the ABS modulator-control unit and the PCM. If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE PCM ), then recheck. If the PCM was substituted, go to step  1. If the HDS indicates NOT COMPLETED, keep idling until a result comes on.

  15. Check the communication line between the ABS modulator-control unit and the gauge control module with the HDS.

    Is there malfunction in the F-CAN line between the ABS modulator-control unit and the gauge control module? 

    YES  - Repair open in the wires between the ABS modulator-control unit connector and the CAN communication lines.

    NO  - Substitute a known-good ABS modulator-control unit (see ABS MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION ), then recheck. If the symptom/indication goes away with a known-good ABS modulator-control unit, replace the original ABS modulator-control unit.

scientia non olet · About LEMON Manuals