DTC U0100: Gauge Control Module Lost Communication With ECM/PCM

1. Clear the DTCs with the HDS.
2. Turn the ignition switch to LOCK (0), and then back to ON (II).
3. Start and run the engine for at least 5 seconds, then turn the engine off.
4. Check for DTCs with the HDS.

   Is DTC U0100 indicated? 

   YES  -Go to step 5.

   NO  -Intermittent failure, the F-CAN communication line is OK at this time. Check for DTCs in the ECM/PCM with the HDS. If F-CAN DTCs are present, check for loose or poor connections at the gauge control module and the ECM/PCM. If the connections are good, check the battery condition (see BATTERY TEST ) and the charging system, then clear all DTCs.

5. Check for DTCs in the ECM/PCM with the HDS.

   Are any DTCs indicated? 

   YES  -Go to the ECM/PCM indicated DTCs troubleshooting, then recheck.

   NO  -Go to step 6.

6. Turn the ignition switch to LOCK (0).
7. Jump the SCS line with HDS.
8. Disconnect ECM/PCM connector A (49P).
9. Check for continuity between gauge control module 32P connector terminals No. 21 and No. 22 and ECM/PCM connector A (49P) terminals No. 4 and No. 3 respectively.

Fig 1: Checking Continuity Between Gauge Control Module 32P Connector Terminals No. 21 And No. 22

Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity? 

YES  -Substitute a known-good ECM/PCM (see ECM/PCM REPLACEMENT ), and recheck. If the indication goes away, replace the original ECM/PCM (see ECM/PCM REPLACEMENT ). If the DTC is still present, replace the gauge control module (see GAUGE CONTROL MODULE REPLACEMENT ).

NO  -Repair an open or poor connection in the wire between the ECM/PCM and the gauge control module.