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 P0139, P0159 [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 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 SERVICE INFORMATION AVAILABILITY Verify related Service Information availability. Is any related Service Information available?	Yes	Perform the repair or diagnosis according to the available Service 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 DTC Turn the ignition switch off, then ON (Engine off). Verify pending and/or stored DTCs using the WDS or equivalent. Is DTC P0443 also present?	Yes	Go to the DTC P0443 troubleshooting procedures, then go to Step 11.
3		No	Go to the next step.
4	IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA Is DTC P0139 or P0159 on FREEZE FRAME DATA?	Yes	Go to the next step.
4		No	Go to the troubleshooting procedures for the DTC in the FREEZE FRAME DATA. (See DTC TABLE .)
5	VERIFY CURRENT INPUT SIGNAL STATUS Warm up the engine. Access O2S12 (with DTC P0139) or O2S22 (with DTC P0159) PID using the WDS or equivalent. Inspect the PID under the following accelerator pedal conditions in PARK (ATX) or NEUTRAL (MTX). Is the PID normal? More than 0.55 V when accelerator pedal is suddenly depressed (rich condition). Less than 0.55 V just after release of the accelerator pedal (lean condition).	Yes	Go to step 7.
5		No	Go to the next step.
6	INSPECT INSTALLATION OF REAR HO2S Inspect for loose the HO2S (LR, RR) installation. Is the sensor installed securely?	Yes	Inspect the HO2S (LR with DTC P0139 or RR with DTC P0159). If normal, go to step 11 If there is a malfunction, replace suddenly depress HO2S, then go to Step 11
6		No	Retighten the sensor, then go to Step 11.
7	INSPECT LONG TERM FUEL TRIM Access the LONGFT1 (with DTC P0139) or LONGFT2 (with DTC P0159) PID Compare it with the FREEZE FRAME DATA recorded in Step 1. Is it below the FFD value?	Yes	Engine is driven under a rich condition. Go to the next step.
7		No	Engine is driven under a lean condition. Go to step 9.
8	INSPECT FUEL LINE PRESSURE (Excessive fuel line pressure) Turn the ignition switch off. Inspect fuel line pressure while the engine is running. (See FUEL LINE PRESSURE INSPECTION .) Is the fuel line pressure normal?	Yes	Go to step 10.
8		No	Inspect the fuel pump maximum pressure and the fuel return pipe for clogging. (See FUEL PUMP UNIT INSPECTION .) If there is any problem, repair or replace the parts. If all items above are normal, replace the fuel pump unit. Then go to Step 11.
9	INSPECT FUEL LINE PRESSURE (Low fuel line pressure) Turn the ignition switch off. Inspect the fuel line pressure while the engine is running. (See FUEL LINE PRESSURE INSPECTION .) Is the fuel line pressure normal?	Yes	Go to step 10.
9		No	Inspect the fuel filters for the following: Foreign material or staining inside the fuel filter (low-pressure side) Perform the following actions according to the result. If foreign material or staining is found inside the fuel filter (low-pressure side), clean the fuel tank and filter. If normal, replace fuel pump unit. Then go to Step 11.
10	INSPECT SEALING OF ENGINE COOLANT PASSAGE Perform "ENGINE COOLANT LEAKAGE INSPECTION." (See ENGINE COOLANT LEAKAGE INSPECTION .) Is there any malfunction?	Yes	Go to the next step.
10		No	Repair or replace the malfunctioning part according to inspection results. Then go to the next step.
11	VERIFY TROUBLESHOOTING OF DTC P0139 OR P0159 COMPLETED Make sure to reconnect all disconnected connectors. Turn the ignition switch to the ON position. (Engine off) Clear the DTC from the memory using the WDS or equivalent. Run Drive Mode 1 and 3 (See OBD-II DRIVE MODE .) Is the PENDING CODE for this DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION .)
11		No	Go to the next step.
12	VERIFY AFTER REPAIR PROCEDURE Perform the "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE .) Are any DTCs present?	Yes	Go to the applicable DTC troubleshooting. (See DTC TABLE .)
12		No	Troubleshooting completed.