DTC U0104: F-CAN A Malfunction (PCM-Adaptive Cruise Control (ACC) Unit)

WARNING: This page is about a different car, the 2013 Acura MDX, 2012 Acura MDX, 2011 Acura MDX, and 2010 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).

Turn the ignition switch to ON (II).
Check for Pending or Confirmed DTCs with the HDS.
Are DTC U0029 and U0104 Indicated at the same time?

YES -Go to the troubleshooting for DTC U0029 (see DTC U0029: F-CAN A Malfunction (BUS-OFF (PCM)) ).

NO -Go to step 3.
Clear the DTC with the HDS.
Check for Pending or Confirmed DTCs with the HDS.
Is DTC U0104 indicated?

YES -Go to step 5.

NO -Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the ACC unit and the PCM.
Check for communication to the DRIVING SUPPORT SYSTEM with the HDS
Does the HDS communicate with the ACC unit?

YES -Go to step 6.

NO -Go to the DLC CIRCUIT TROUBLESHOOTING
Turn the ignition switch to LOCK (0).
Jump the SCS line with the HDS.
Disconnect the ACC unit 20P connector.
Disconnect PCM connector A (49P).
Check for continuity between PCM connector terminal A48 and ACC unit 20P connector terminal No. 10.

Fig 1: Checking Continuity Between PCM Connector Terminal A48 And ACC Unit 20P Connector Terminal No. 10
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Go to step 11.

NO -Repair an open in the wire between the PCM (A48) and the ACC unit, then go to step 12.
Check for continuity between PCM connector terminal A49 and ACC unit 20P connector terminal No. 20.

Fig 2: Checking Continuity Between PCM Connector Terminal A49 And ACC Unit 20P Connector Terminal No. 20
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Substitute a known-good ACC unit (see ADAPTIVE CRUISE CONTROL (ACC) UNIT REMOVAL/INSTALLATION ), then go to step 12 and recheck. If DTC U0104 is not indicated after substitution, replace the original ACC unit (see ADAPTIVE CRUISE CONTROL (ACC) UNIT REMOVAL/INSTALLATION ), then go to step 12.

NO -Repair an open in the wire between the PCM (A49) and the ACC unit, then go to step 12.
Reconnect all connectors.
Turn the ignition switch to ON (II).
Reset the PCM with the HDS.
Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
Check for Pending or Confirmed DTCs with the HDS.
Is DTC U0104 indicated?

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

NO -Troubleshooting is complete. If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC'S TROUBLESHOOTING .