DTC Troubleshooting: U0121 (107-7)
|DTC U0121:||Lost Communication with ABS Modulator-Control Unit|
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 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?
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