Diagnostic Procedure

WARNING: This page is about a different car, the 2014 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

DTC U0402:00 (VEHICLE CONTROL MODULE) DIAGNOSTIC PROCEDURE

Step	Inspection		Action
1	PERFORM DTC INSPECTION FOR TCM Perform the TCM DTC inspection using the M-MDS. (See ON-BOARD DIAGNOSTIC SYSTEM DTC INSPECTION [FW6A-EL] .) Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See ON-BOARD DIAGNOSTIC SYSTEM DTC TABLE [FW6A-EL] .) Then go to Step 3.
1		No	Go to the next step.
2	PERFORM DTC INSPECTION FOR VEHICLE CONTROL MODULE (V/C-MODULE) Clear vehicle control module (V/C-module) DTCs using the M-MDS. (See CLEARING DTC [VEHICLE CONTROL MODULE (V/C-MODULE)] .) Switch the ignition ON (engine on). Perform the vehicle control module (V/C-module) DTC inspection using the M-MDS. (See DTC INSPECTION [VEHICLE CONTROL MODULE (V/C-MODULE)] .) Is the same DTC present?	Yes	Replace the TCM, then go to the next step. (See CONTROL VALVE BODY REMOVAL/INSTALLATION .)
2		No	Go to the next step.
3	VERIFY THAT REPAIRS HAVE BEEN COMPLETED Clear vehicle control module (V/C-module) DTCs using the M-MDS. (See CLEARING DTC [VEHICLE CONTROL MODULE (V/C-MODULE)] .) Switch the ignition ON (engine on). Perform the vehicle control module (V/C-module) DTC inspection using the M-MDS. (See DTC INSPECTION [VEHICLE CONTROL MODULE (V/C-MODULE)] .) 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 vehicle control module (V/C-module). (See VEHICLE CONTROL MODULE (V/C-MODULE) REMOVAL/INSTALLATION [MAZDA RADAR CRUISE CONTROL (MRCC) SYSTEM] .) 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.