DTC U0122: F-CAN Malfunction (VSA Modulator-Control Unit-PCM)

NOTE:

Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
If DTC U0073 is stored at the same time as DTC U0122, troubleshoot DTC U0073 first, then recheck for DTC U0122.

Turn the ignition switch ON (II).
Clear the DTC with the HDS.
Check for Temporary DTCs or DTCs with the HDS.
Is DTC U0122 indicated?
1. YES - Go to step 4.
2. NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the gauge assembly, the VSA modulator-control unit and the PCM.
Check for a DTC in the DTCs MENU with the HDS.
Is VSA DTC 86 indicated?
1. YES - Go to step 5.
2. NO - Go to step 9.
Turn the ignition switch OFF.
Disconnect the VSA modulator-control unit 47P connector.
Check for continuity between VSA modulator-control unit 47P connector terminals No. 3 and No. 18.

Fig 1: Checking Continuity Between VSA Modulator-Control Unit 47P Connector Terminals 3 And 18
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES - Go to step 8.
2. NO - Repair open in the wire between the VSA modulator-control unit (No. 3 (No. 18)*) and the PCM (B16 (B15)*), then go to step 14.
  *: CANL line
Check for poor connection at left engine compartment wire harness/dashboard wire harness A 14P connector.
Is it OK?
1. YES - Substitute a known-good VSA modulator-control unit, then go to step 14 and recheck. If no DTC is indicated, replace the original VSA modulator-control unit, then go to step 14.
2. NO - Reconnect the left engine compartment wire harness/dashboard wire harness A 14P connector, then go step 14.
Turn the ignition switch OFF.
Disconnect the VSA modulator-control unit 47P connector.
Turn the ignition switch ON (II).
Measure voltage between VSA modulator-control unit 47P connector terminal No. 38 and body ground.

Fig 2: Measuring Voltage Between VSA Modulator-Control Unit 47P Connector Terminal 38 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?
1. YES - Go to step 13.
2. NO - Check the No. 9 IG METER (10 A) fuse in the driver's under-dash fuse/relay box. If the fuse is OK, repair open in the wire between the No. 10 IG METER (10 A) fuse and the VSA modulator-control unit, then go to step 14.
Check for continuity between VSA modulator-control unit 47P connector terminal No. 32 and body ground.

Fig 3: Checking Continuity Between VSA Modulator-Control Unit 47P Connector Terminal 32 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES - Substitute a known-good VSA modulator-control unit, then go to step 14 and recheck. If no DTC is does not indicated, replace the original VSA modulator-control unit, then go to step 14.
2. NO - Repair open in the wire between the VSA modulator-control unit and G302, then go to step 14.
Turn the ignition switch ON (II).
Clear the DTC with the HDS.
Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
Check for Temporary DTCs or DTCs with the HDS.
Are any Temporary DTCs or DTCs indicated?
1. YES - If DTC U0122 is indicated, check for poor connections or loose terminals at the gauge assembly, the VSA modulator-control unit and the PCM, then go to step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
2. NO - Troubleshooting is complete.