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

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.
Information marked with an asterisk (*) applies to the CANL line.

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?

YES -Go to step 4.

NO -Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the VSA modulator-control unit and the PCM.
Check for a VSA system DTCs in the DTCs MENU with the HDS.
Is VSA DTC 86 indicated?

YES -Go to step 5.

NO -Go to step 10.
Turn the ignition switch OFF.
Jump the SCS line with the HDS.
Disconnect PCM connector A (44P).
Disconnect the VSA modulator-control unit 47P connector (see VSA MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION ).
Check for continuity between PCM connector terminal A36 and VSA modulator-control unit 47P connector terminals No. 14, and between PCM connector terminal A1 * and VSA modulator-control unit 47P connector terminal No. 30*.

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

Is there continuity?

YES -Substitute a known-good VSA modulator-control unit (see VSA MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION ), then go to step 15 and recheck. If DTC U0122 is not indicated, replace the original VSA modulator-control unit (see VSA MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION ), then go to step 17.

NO -Repair open in the wire between the VSA modulator-control unit (No. 14 (No. 30)*) and the PCM (A36 (A1)*), then go to step 17.
Check for poor connections at the left engine compartment wire harness/dashboard wire harness 18P connector and the VSA modulator-control unit 47P connector.
Are the connections OK?

YES -Go to step 11.

NO -Repair the connections, then go step 17.
Turn the ignition switch OFF.
If not already done, disconnect the VSA modulator-control unit 47P connector (see VSA MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION ).
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 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Go to step 15.

NO -Check the No. 6 FI-ECU (15 A) fuse in the driver's under-dash fuse relay box. If the fuse is OK, repair open in the wire between the No. 6 FI-ECU (15 A) fuse and the VSA modulator-control unit, then go to step 16.
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 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Substitute a known-good VSA modulator-control unit (see VSA MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION ), then go to step 17 and recheck. If DTC U0122 is not indicated, replace the original VSA modulator-control unit (see VSA MODULATOR-CONTROL UNIT REMOVAL AND INSTALLATION ), then go to step 17.

NO -Repair open in the wire between the VSA modulator-control unit and G302, then go to step 17.
Turn the ignition switch OFF.
Reconnect all connectors.
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.
Is DTC U0122 indicated?

YES -Check for poor connections or loose terminals at the VSA modulator-control unit and the PCM, then go to step 1.

NO -Troubleshooting is complete. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.