Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0031 [AJ] DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED Have FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (HO2S heater related) been recorded?	Yes	Go to the next step.
1		No	Record FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS 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 HO2S (RF) CONNECTOR FOR POOR CONNECTION Turn the ignition switch off. Disconnect HO2S (RF) connector. Check for poor connection (such as damaged, pulled-out pins, and corrosion). Is there any malfunction?	Yes	Repair or replace the terminal, then go to Step 9.
3		No	Go to the next step.
4	INSPECT HO2S HEATER (RF) POWER CIRCUIT FOR OPEN CIRCUIT Turn the ignition switch to the ON position. Measure voltage between HO2S (RF) terminal C (harness-side) and body GND. Is voltage B+?	Yes	Go to the next step.
4		No	Repair or replace harness for open circuit, then go to Step 9.
5	INSPECT HO2S HEATER (RF) CONTROL CIRCUIT FOR SHORT TO GND Turn the ignition switch off. Check continuity between HO2S (RF) terminal D (harness-side) and body GND. Is there continuity?	Yes	Repair or replace harness for short to GND, then go to Step 9.
5		No	Go to the next step.
6	INSPECT HO2S HEATER (RF) Inspect HO2S heater (RF). (See HEATED OXYGEN SENSOR (HO2S) INSPECTION .) Is there any malfunction?	Yes	Replace HO2S (RF), then go to Step 9. (See EXHAUST SYSTEM REMOVAL/INSTALLATION .)
6		No	Go to the next step.
7	INSPECT PCM CONNECTOR FOR POOR CONNECTION Turn the ignition switch off. Disconnect PCM connector. Check for poor connection (such as damaged, pulled-out pins, and corrosion). Is there any malfunction?	Yes	Repair or replace the terminal, then go to Step 9.
7		No	Go to the next step.
8	INSPECT HO2S HEATER (RF) CONTROL CIRCUIT FOR OPEN CIRCUIT Turn the ignition switch off. Check continuity between HO2S (RF) terminal D (harness-side) and PCM terminal 83 (harness-side). Is there continuity?	Yes	Go to the next step.
8		No	Repair or replace harness for open circuit, then go to Step 9.
9	VERIFY TROUBLESHOOTING OF DTC P0031 COMPLETED Make sure to reconnect all disconnected connectors. Clear the DTC from the PCM memory using the WDS or equivalent. Start engine and warm up it completely. Is PENDING CODE same as DTC present?	Yes	Replace PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION .)
9		No	Go to the next step.
10	VERIFY AFTER REPAIR PROCEDURE Perform "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE .) Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE .)
10		No	Troubleshooting completed.