DTC U0401:68

Signal error from PCM

DETECTION CONDITION

• When any of the following conditions is met:

• PCM internal malfunction

• CAN communication line between PCM and DC-DC converter malfunction

FAIL-SAFE FUNCTION

• Not applicable

POSSIBLE CAUSE

• CAN drive error (DC-DC converter or PCM)

• CAN communication line between PCM and DC-DC converter malfunction

• PCM terminal 2AK—Front body control module (FBCM) terminal 2P

• PCM terminal 2AL—Front body control module (FBCM) terminal 2N

• Front body control module (FBCM) terminal 2K—DC-DC converter terminal 1A

• Front body control module (FBCM) terminal 2I—DC-DC converter terminal 1C

• Front body control module (FBCM) malfunction

• DC-DC converter connector or terminals malfunction

• PCM connector or terminals malfunction

• DC-DC converter malfunction

• PCM malfunction

STEP

INSPECTION

ACTION

1

• Verify related Service Bulletins and/or on-line repair information availability.

• Is any related repair information available?

Yes

Perform repair or diagnosis according to the available repair information.

• If the vehicle is not repaired, go to the next step.

No

Go to the next step.

2

• Switch the ignition off, then ON (engine off).

• Retrieve the PCM DTCs using the M-MDS.

  (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.5].)

• Are any DTCs present?

Yes

Repair or replace the malfunctioning part according to the applicable DTC troubleshooting.

(See DTC TABLE [SKYACTIV-G 2.5].)

No

Go to the next step.

3

• Perform the front body control module (FBCM) DTC inspection using the M-MDS.

  (See DTC INSPECTION [FRONT BODY CONTROL MODULE (FBCM)].)

• Are any DTCs present?

Yes

Repair or replace the malfunctioning part according to the applicable DTC troubleshooting.

(See DTC TABLE [FRONT BODY CONTROL MODULE (FBCM)].)

No

Go to the next step.

4

• Perform the instrument cluster DTC inspection using the M-MDS.

  (See DTC INSPECTION [INSTRUMENT CLUSTER].)

• Are any DTCs present?

Yes

Repair or replace the malfunctioning part according to the applicable DTC troubleshooting.

(See DTC TABLE [INSTRUMENT CLUSTER].)

No

Go to the next step.

5

• Switch the ignition off.

• Disconnect the negative battery cable.

  (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.5].)

• Disconnect the service plug.

  (See SERVICE PLUG DISCONNECTION/CONNECTION [i-ELOOP].)

• Disconnect the DC-DC converter connector.

• Inspect for poor connection (such as damaged/pulled-out pins, corrosion).

• Is there any malfunction?

Yes

Repair or replace the connector and/or terminals, then go to Step 7.

No

Go to the next step.

6

• Disconnect the PCM connector.

• Inspect for poor connection (such as damaged/pulled-out pins, corrosion).

• Is there any malfunction?

Yes

Repair or replace the connector and/or terminals, then go to the next step.

No

CAN communication line can be considered the cause.

• Refer to the wiring diagram and verify whether or not there is a common connector between the following terminals:

• PCM terminal 2AK—Front body control module (FBCM) terminal 2P

• PCM terminal 2AL—Front body control module (FBCM) terminal 2N

• Front body control module (FBCM) terminal 2K—DC-DC converter terminal 1A

• Front body control module (FBCM) terminal 2I—DC-DC converter terminal 1C

If there is a common connector:

• Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a malfunction.

• Repair or replace the malfunctioning part.

If there is no common connector:

• Repair or replace the wiring harness.

If the malfunction recurs, replace the DC-DC converter.

(See DC-DC CONVERTER REMOVAL/INSTALLATION [i-ELOOP].)

Go to the next step.

7

• Always reconnect all disconnected connectors.

• Reconnect the negative battery cable.

  (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.5].)

• Reconnect the service plug.

  (See SERVICE PLUG DISCONNECTION/CONNECTION [i-ELOOP].)

• Clear the DTC for the DC-DC converter using the M-MDS.

  (See CLEARING DTC [i-ELOOP].)

• Switch the ignition off.

• Switch the ignition ON (engine off) and wait for 5 s or more.

• Retrieve the DC-DC converter DTCs using the M-MDS.

  (See DTC INSPECTION [i-ELOOP].)

• Is the same DTC present?

Yes

Repeat the inspection from Step 1.

• If the malfunction recurs, replace the PCM.

  (See PCM REMOVAL/INSTALLATION [SKYACTIV-G 2.5].)

Go to the next step.

No

Go to the next step.

8

• Are any other DTCs displayed?

Yes

Repair or replace the malfunctioning part according to the applicable DTC troubleshooting.

(See DTC TABLE [i-ELOOP].)

No

DTC troubleshooting completed.