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 P0140 [L3] 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 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	VERIFY RELATED PENDING AND STORED DTCS NOTE: If fuel monitor DTC, DTC P0131 or P0132 is retrieved, ignore it until P0140 is fixed. Turn ignition switch to OFF, then ON (Engine off). Verify pending and stored DTCs using the WDS or equivalent. Is other DTC present?	Yes	Go to appropriate DTC troubleshooting procedures. (See DTC TABLE .)
3		No	Go to the next step.
4	IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA Is DTC P0140 on FREEZE FRAME DATA?	Yes	Go to the next step.
4		No	Go to troubleshooting procedures for DTC on FREEZE FRAME DATA. (See DTC TABLE .)
5	VERIFY CURRENT INPUT SIGNAL STATUS Warm up engine. Access O2S12 for P0140 or O2S22 for P0160 PID using the WDS or equivalent. Verify PID while racing engine at least 10 times (in NEUTRAL (MTX) or PARK (ATX)). Is PID reading normal? - More than 0.55 V at least once during engine racing	Yes	Go to step 8.
5		No	Go to the next step.
6	INSPECT INSTALLATION OF REAR HO2S Check if rear HO2S is loosely installed. Is sensor installed securely?	Yes	Go to the next step.
6		No	Install sensor securely, then go to Step 10.
7	INSPECT GAS LEAKAGE FROM EXHAUST SYSTEM Visually check if any gas leakage is found between exhaust pipe and rear HO2S. Is there gas leakage?	Yes	Repair or replace any malfunctioning exhaust parts, then go to Step 10.
7		No	Inspect the following harnesses for open or short to ground circuit, repair or replace harness if necessary. Rear HO2S terminal A (harness-side) to PCM terminal 1Y (harness-side) Repair or replace harness if necessary. If all items above are normal, replace faulty sensor. Then go to Step 10.
8	INSPECT SEALING OF ENGINE COOLANT PASSAGE WARNING: Removing radiator cap when radiator is hot is dangerous. Scalding coolant and steam may shoot out and cause serious injury. When removing radiator cap, wrap a thick cloth around and turn it slowly. Remove radiator cap. Implement procedure to bleed air from engine coolant, then run engine at idle. Is there any small bubble, which makes engine coolant white at filling opening? NOTE: Large bubbles are normal since they are remaining air coming out from engine coolant passage.	Yes	Air gets in from poor sealing on head gasket or other areas between combustion chamber and engine coolant passage. Repair or replace faulty parts, then go to Step 10.
8		No	Go to the next step.
9	INSPECT ENGINE COMPRESSION Inspect engine compression. (See COMPRESSION INSPECTION .) Is it normal?	Yes	Go to the next step.
9		No	Implement engine overhaul for repairs, then go to the next step.
10	VERIFY TROUBLESHOOTING OF DTC P0140 COMPLETED Make sure to reconnect all disconnected connectors. Clear the DTC from the PCM memory using the WDS or equivalent. Turn the ignition switch off. Start engine and warm it up completely. Is PENDING CODE for this DTC present?	Yes	Replace PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION .)
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.