DTC U128D: Immobilizer-Keyless Control Unit Lost Communication With Gauge Control Module

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).
Wait for at least 6 seconds.
Check for DTCs with the HDS.
Is DTC U128D indicated?

YES -Go to step 5.

NO -Intermittent failure, the system is OK at this time. Check for loose or poor connections between the immobilizer-keyless 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 gauge control module detected?

YES -Go to step 10.

NO -Go to step 6.
Measure the voltage between body ground and gauge control module 32P connector terminals No. 1 and No. 17 individually.

Fig 1: Measuring Voltage Between Body Ground And Gauge Control Module 32P Connector Terminals No. 1 And No. 17
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Go to step 9.

NO -Go to step 7.
Turn the ignition switch to LOCK (0).
Check the No. B16(10 A) fuse in the under-hood fuse/relay box and the No. C11 (7.5 A) fuse in the driver's under-dash fuse/relay box.
Are the fuses OK?

YES -Repair an open or high resistance in the No. B16 (10 A) and/or No. C11 (7.5 A) fuse circuit.

NO -Replace the fuse(s). If the fuse blows again, repair a short to ground in the No. B16 (10 A) and/or No. C11 (7.5 A) fuse circuit.
Measure the voltage between body ground and gauge control module 32P connector terminal No. 4.

Fig 2: Measuring Voltage Between Body Ground And Gauge Control Module 32P Connector Terminal No. 4
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 or poor ground (G401).
Turn the ignition switch to LOCK (0).
Disconnect the immobilizer-keyless control unit 7P connector.
Disconnect the gauge control module 32P connector.
Check for continuity between immobilizer-keyless control unit 7P connector terminals No. 4 and No. 5 and gauge control module 32P connector terminals No. 29 and No. 30 respectively.

Fig 3: Checking Continuity Between Immobilizer-Keyless Control Unit Connector Terminals And Gauge Control Module Connector Terminals
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Replace the gauge control module (see GAUGE CONTROL MODULE REPLACEMENT ).

NO -An open or poor connection in the B-CAN wire between the immobilizer-keyless control unit and the gauge control module.