Diagnostic Procedure

WARNING: This page is about a different car, the 2020 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.

DTC U0401:64 (RETRACTABLE HARDTOP CONTROL MODULE) DIAGNOSTIC PROCEDURE

Step	Inspection		Action
1	VERIFY PCM DTCs Retrieve the PCM DTCs using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [PCM (SKYACTIV-G 2.0)] .) Are any DTCs displayed?	Yes	Repair or replace the malfunctioning part according to the applicable DTC troubleshooting. (See DTC TABLE [PCM (SKYACTIV-G 2.0)] .)
1		No	Go to the next step.
2	VERIFY IF MALFUNCTIONING LOCATION IS PCM DEPENDING ON REPEATABILITY Clear the DTC for the retractable hardtop control module using the M-MDS. (See CLEARING DTC [RETRACTABLE HARDTOP CONTROL MODULE] .) Retrieve the retractable hardtop control module DTCs using the M-MDS. (See DTC INSPECTION [RETRACTABLE HARDTOP CONTROL MODULE] .) Is the same Pending DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [SKYACTIV-G 2.0] .)
2		No	Go to Step 4.
3	VERIFY THAT REPAIRS HAVE BEEN COMPLETED Clear the DTC for the retractable hardtop control module using the M-MDS. (See CLEARING DTC [RETRACTABLE HARDTOP CONTROL MODULE] .) Retrieve the retractable hardtop control module DTCs using the M-MDS. (See DTC INSPECTION [RETRACTABLE HARDTOP CONTROL MODULE] .) Is the same Pending DTC present?	Yes	Repeat the inspection from Step 1. If the malfunction recurs, replace the retractable hardtop control module. (See RETRACTABLE HARDTOP CONTROL MODULE REMOVAL/INSTALLATION .) Go to the next step.
3		No	Go to the next step.
4	VERIFY IF OTHER DTCs DISPLAYED Are any other DTCs displayed?	Yes	Repair or replace the malfunctioning part according to the applicable DTC troubleshooting. (See DTC TABLE [RETRACTABLE HARDTOP CONTROL MODULE] .)
4		No	DTC troubleshooting completed.