Diagnostic Procedure

WARNING: This page is about a different car, the 2018 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

DTC U0420:00 RADAR UNIT DIAGNOSTIC PROCEDURE

Step	Inspection		Action
1	PERFORM DTC INSPECTION FOR EPS CONTROL MODULE Perform the EPS control module DTC inspection using the M-MDS. (See DTC INSPECTION [ELECTRIC POWER STEERING (EPS)] .) Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [ELECTRIC POWER STEERING (EPS)] .) Go to Step 3.
1		No	Go to the next step.
2	VERIFY IF MALFUNCTIONING LOCATION IS EPS CONTROL MODULE DEPENDING ON REPEATABILITY 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 Pending DTC present?	Yes	Replace the EPS control module, then go to the next step. (See STEERING WHEEL AND COLUMN REMOVAL/INSTALLATION .)
2		No	Go to Step 4.
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 Pending 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.