DTC U128B: Gauge Control Module Lost Communication With Power Control Unit

NOTE: If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A (see TROUBLESHOOTING - B-CAN SYSTEM DIAGNOSIS TEST MODE A ).

Clear the DTCs with the HDS.
Turn the ignition switch to LOCK (0) and then back to ON (II), or press the engine start/stop button to select the OFF mode and then the ON mode.
Wait for at least 6 seconds.
Check for DTCs with the HDS.
Is DTC U128B indicated?

YES -Go to step 5.

NO -Intermittent failure, the system is OK at this time. Check for loose or poor connections between the power control unit and the gauge control module.
From the BODY ELECTRICAL SYSTEM SELECT menu, select B-CAN CONTROL UNITS INFORMATION, and then select CHECK CONNECTED CONTROL UNITS.
Is the power control unit detected?

YES -Go to step 9.

NO -Go to step 6.
Measure the voltage between body ground and power control unit connector C (36P) terminal No. 1.

Fig 1: Measuring Voltage Between Body Ground And Power Control Unit Connector C (36P) Terminal No. 1
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Go to step 8.

NO -Go to step 7.
Check the No. 15(10 A) fuse in the under-hood fuse/relay box.
Is the fuse OK?

YES -Repair an open or high resistance in the No. 15 (10A) fuse circuit.

NO -Replace the fuse. If the fuse blows again, repair a short to ground in the No. 15 (10 A) fuse circuit.
Measure the voltage between body ground and power control unit connector C(36P) terminals No. 18 and No. 36 individually.

Fig 2: Measuring Voltage Between Body Ground And Power Control Unit Connector C(36P) Terminals No. 18 And No. 36
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there less than 0.2 V?

YES -Go to step 9.

NO -Repair an open or high resistance in the ground wire or poor ground (G402).
Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.
Disconnect power control unit connector C (36P).
Disconnect the gauge control module 32P connector.
Check for continuity between gauge control module 32P connector terminals No. 29 and No. 30 and power control unit connector C (36P) terminals No. 17 and No. 16 respectively.

Fig 3: Checking Continuity Between Gauge Control Module 32P Connector And Power Control Unit Connector C (36P)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Replace the power control unit (see RF UNIT REPLACEMENT ).

NO -Repair an open or poor connection in the B-CAN wire between the power control unit and the gauge control module.