| DTC U0121: | Lost Communication with ABS Modulator-Control Unit |
| 1. | Clear the DTC with the HDS. |
| 2. | Turn the ignition switch ON (II). |
| 3. | Check that DTC U0121 recurs. Is DTC U0121 indicated? YES - Go to 4. NO - Intermittent failure, the system is OK at this time.n |
| 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 for indicated DTC in the ABS. NO - Go to 5. |
| 5. | Turn the ignition switch OFF. |
| 6. | Jump the SCS line with the HDS. |
| 7. | Disconnect PCM connector A (44P). |
| 8. | Disconnect the ABS modulator-control unit 25P connector. |
| 9. | Check for continuity between PCM connector terminal A36 and ABS modulator-control unit 25P connector terminal No. 1, and between A37 and terminal No. 17.
Is there continuity? YES - Update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM.n NO - Go to 10. |
| 10. | Check the communication line between the ABS modulator-control unit and gauge control module by the HDS. Is there malfunction in the F-CAN line between the ABS modulator-control unit and gauge control module? YES - Repair open in the wires between ABS modulator-control unit 25P connector and CAN communication lines.n NO - Substitute a known-good ABS modulator-control unit, then recheck. If the symptom/indication goes away with a known-good ABS modulator-control unit, replace the original ABS modulator-control unit.n |