DTC U0401:00 [RADAR UNIT]

id1502a6019200

System malfunction location

Error signal received from PCM

Detection condition

•  Communication error between PCM and radar unit

Fail-safe

•  Inhibits the Mazda radar cruise control (MRCC) system control

Possible cause

•  PCM malfunction (engine speed signal malfunction)

•  Radar unit malfunction

System wiring diagram

•  Not applicable

System malfunction location	Error signal received from PCM
Detection condition	• Communication error between PCM and radar unit
Fail-safe	• Inhibits the Mazda radar cruise control (MRCC) system control
Possible cause	• PCM malfunction (engine speed signal malfunction) • Radar unit malfunction
System wiring diagram	• Not applicable

Diagnostic Procedure

Step

Inspection

Action

1

PERFORM DTC INSPECTION FOR PCM

•  Perform the PCM DTC inspection using the M-MDS.
(See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.0, SKYACTIV-G 2.5].)

•  Are any DTCs present?

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [SKYACTIV-G 2.0, SKYACTIV-G 2.5].)

Then go to Step 3.

No

Go to the next step.

2

PERFORM DTC INSPECTION FOR RADAR UNIT

•  Clear radar unit DTCs using the M-MDS.
(See CLEARING DTC [RADAR UNIT].)

•  Switch the ignition ON (engine on).

•  Perform the radar unit DTC inspection using the M-MDS.
(See DTC INSPECTION [RADAR UNIT].)

•  Is the same DTC present?

Yes

Replace the radar unit, then go to the next step.

(See RADAR UNIT REMOVAL/INSTALLATION.)

No

Go to the next step.

3

VERIFY THAT REPAIRS HAVE BEEN COMPLETED

•  Clear radar unit DTCs using the M-MDS.
(See CLEARING DTC [RADAR UNIT].)

•  Switch the ignition ON (engine on).

•  Perform the radar unit DTC inspection using the M-MDS.
(See DTC INSPECTION [RADAR UNIT].)

•  Is the same DTC present?

Yes

Repeat the inspection from Step 1.

•  If the malfunction does not recur, go to the next step.

•  If the malfunction recurs, replace the radar unit.
(See RADAR UNIT REMOVAL/INSTALLATION.)

Go to the next step.

No

Go to the next step.

4

VERIFY THAT NO OTHER DTCs ARE PRESENT

•  Verify other DTCs displayed.

•  Are any other DTCs output?

Yes

Perform the corresponding DTC inspection.

No

DTC troubleshooting completed.

Step	Inspection		Action
1	PERFORM DTC INSPECTION FOR PCM • Perform the PCM DTC inspection using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) • Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) Then go to Step 3.
1		No	Go to the next step.
2	PERFORM DTC INSPECTION FOR RADAR UNIT • Clear radar unit DTCs using the M-MDS. (See CLEARING DTC [RADAR UNIT].) • Switch the ignition ON (engine on). • Perform the radar unit DTC inspection using the M-MDS. (See DTC INSPECTION [RADAR UNIT].) • Is the same DTC present?	Yes	Replace the radar unit, then go to the next step. (See RADAR UNIT REMOVAL/INSTALLATION.)
2		No	Go to the next step.
3	VERIFY THAT REPAIRS HAVE BEEN COMPLETED • Clear radar unit DTCs using the M-MDS. (See CLEARING DTC [RADAR UNIT].) • Switch the ignition ON (engine on). • Perform the radar unit DTC inspection using the M-MDS. (See DTC INSPECTION [RADAR UNIT].) • Is the same DTC present?	Yes	Repeat the inspection from Step 1. • If the malfunction does not recur, go to the next step. • If the malfunction recurs, replace the radar unit. (See RADAR UNIT REMOVAL/INSTALLATION.) Go to the next step.
3		No	Go to the next step.
4	VERIFY THAT NO OTHER DTCs ARE PRESENT • Verify other DTCs displayed. • Are any other DTCs output?	Yes	Perform the corresponding DTC inspection.
4		No	DTC troubleshooting completed.