DTC U0121: Lost Communication with ABS Modulator-Control Unit
- Turn the ignition switch ON (II).
- Clear the DTC with the HDS.
- Check for DTCs in the A/T SYSTEM with the HDS.
Is DTC U0121 indicated in the A/T SYSTEM?
YES -Go to step 4.
NO -Intermittent failure, the system is OK at this time.
- Check for Temporary DTCs or DTCs in the PGM-FI SYSTEM with the HDS.
Is DTC U0155 indicated in the PGM-FI SYSTEM?
YES -Go to the DTC U0155 troubleshooting in the PGM-FI system (see DTC U0155: F-CAN MALFUNCTION (ECM/PCM-GAUGE CONTROL MODULE) ).
NO -Go to step 5.
- Check for DTCs in the ABS with the HDS.
Is any DTC indicated in the ABS?
YES -Go to the INDICATED DTC'S TROUBLESHOOTING in the ABS.
NO -Go to step 6.
- Turn the ignition switch OFF.
- Jump the SCS line with the HDS.
- Disconnect PCM connector A (44P).
- Disconnect the ABS modulator-control unit 25P connector.
- Check for continuity between PCM connector terminal A36 and ABS modulator-control unit 25P connector terminal No. 1, and between PCM connector terminal A37 and ABS modulator-control unit 25P connector terminal No. 17.Fig 1: Checking Continuity Between PCM A36 And ABS Modulator-Control Unit 25P Connector Terminal No. 1
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES -Go to step 11.
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.
- Update the PCM if it does not have the latest software (see UPDATING THE PCM ), or substitute a known- good PCM (see SUBSTITUTING THE PCM ).
- Turn the ignition switch ON (II).
- Check for DTC's the A/T SYSTEM with the HDS.
Is DTC U0121 indicated in the A/T SYSTEM?
YES -Check for poor connections or loose terminals at the PCM. If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE PCM ), then go to step 6. If the PCM was substituted, go to step 1.
NO -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, go to the INDICATED DTC'S TROUBLESHOOTING .