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.
Press the engine start/stop button to select the OFF, ACC, and 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 10.

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 9.

NO -Go to step 7.
Press the engine start/stop button to select the OFF mode.
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 (10 A) fuse circuit.

NO -Replace the fuse. If the fuse blows again, repair a short to ground on 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 10.

NO -Repair an open or high resistance in the ground wire(s) or poor ground (G401).
Press the engine start/stop button to select the OFF mode.
Disconnect power control unit connector C (36P).
Disconnect gauge control module connector A (32P).
Check for continuity between gauge control module connector A (32P) terminals No. 29 and No. 30 and power control unit connector C (36P) terminals No. 17 and No. 16 respectively.

Fig 3: Checking For Continuity Between Gauge Control Module Connector A (32P) Terminals No. 29 And No. 30 And Power Control Unit Connector C (36P) Terminals No. 17 And No. 16
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Replace the power control unit (see RF UNIT 1 REPLACEMENT ).

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