Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0401 [BP, BP WITH TC] DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA HAS BEEN RECORDED Has FREEZE FRAME DATA been recorded?	Yes	Go to the next step.
1		No	Record FREEZE FRAME DATA on repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Check for related Service Bulletins and/or online 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.
2		No	Go to the next step.
3	INSPECT FOR OTHER DTCS Turn the ignition switch off, then to the ON position (Engine off). Have other DTCs been stored?	Yes	Repair circuit malfunction for applicable DTCs.
3		No	Go to the next step.
4	INSPECT VACUUM HOSE CONDITION Inspect vacuum hoses for clogs, damage, freezing, or vacuum leakage. Is there any malfunction?	Yes	Replace vacuum hoses, then go to Step 10.
4		No	Go to the next step.
5	INSPECT EGR VALVE MALFUNCTION Inspect EGR valve. Is EGR valve okay?	Yes	Go to the next step.
5		No	Replace EGR valve, then go to Step 10.
6	INSPECT EGR BOOST SENSOR (BP), BARO/MAP SENSOR (BP WITH TC) Inspect the EGR boost sensor (BP), BARO/MAP sensor (BP WITH TC). (See EGR BOOST SENSOR (BP), BAROMETRIC PRESSURE (BARO)/MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR (BP WITH TC) INSPECTION [BP, BP WITH TC] .) Is there any malfunction?	Yes	Replace the EGR boost sensor (BP), BARO/MAP sensor (BP WITH TC), then go to Step 10.
6		No	Go to the next step.
7	INSPECT EGR BOOST SENSOR SOLENOID VALVE Inspect EGR boost sensor solenoid valve. Is EGR boost sensor solenoid valve okay?	Yes	Replace EGR boost sensor solenoid valve, then go to Step 10.
7		No	Go to the next step.
8	INSPECT EGR VALVE PASSAGE Turn the ignition switch off. Remove EGR valve. Is gasket installation normal?	Yes	Go to the next step.
8		No	Install gasket correctly, then go to the next step.
9	MONITOR EGR SYSTEM BY DRIVE MODE Run Drive Mode 1 and Mode 2. Check EGR System Monitor completion status using On-Board Readiness Test function. Has EGR system been monitored?	Yes	Go to the next step.
9		No	Retry this step.
10	VERIFY TROUBLESHOOTING OF DTC P0401 COMPLETED Make sure to connect all disconnected connectors. Turn the ignition switch to the ON position (Engine off). Clear the DTC from the PCM memory using the WDS or equivalent. Start the engine. Is same DTC present?	Yes	Replace PCM, then go to the next step.
10		No	Go to the next step.
11	VERIFY AFTER REPAIR PROCEDURE Perform the "AFTER REPAIR PROCEDURE ". (See AFTER REPAIR PROCEDURE .) Is any DTC present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE .)
11		No	Troubleshooting completed.