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 P0138, P0158 [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 REPAIR INFORMATION AVAILABILITY Check for related Service Bulletins and/or online repair information availability. Is any related repair information available?	Yes	Perform the 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 OR STORED DTCS Turn the ignition switch off, then ON (Engine off). Verify pending code or stored DTCs using the WDS or equivalent. Are other DTCs present?	Yes	Go to the appropriate DTC troubleshooting procedures. (See DTC TABLE .)
3		No	Go to the next step.
4	IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA Is DTC P0138 or P0158 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	INSPECT HO2S (RR, LR) SIGNAL CIRCUIT FOR SHORT TO POWER SUPPLY Turn the ignition switch off. Disconnect the HO2S (RR, LR) connector. Turn the ignition switch to the to ON position (Engine off). Measure the voltage between the following terminals. For P0138: HO2S (RR) terminal A (harness-side) and body ground For P0158: HO2S (LR) terminal A (harness-side) and body ground Is there any voltage?	Yes	Replace short to power supply, then go to Step 7.
5		No	Go to the next step.
6	INSPECT HO2S (RR, LR) Perform the "HEATED OXYGEN SENSOR (HO2S) INSPECTION". (See HEATED OXYGEN SENSOR (HO2S) INSPECTION .) Is the front HO2S normal?	Yes	Go to the next step.
6		No	Replace the sensor, then go to the next step.
7	VERIFY TROUBLESHOOTING OF DTC P0138 OR P0158 COMPLETED Make sure to reconnect all disconnected connectors. Turn the ignition switch to the to ON position (Engine off). Clear the DTC from the PCM 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 .)
7		No	Go to the next step.
8	VERIFY AFTER REPAIR PROCEDURE Perform the "After Repair Procedure". (See AFTER REPAIR PROCEDURE .) Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE ,)
8		No	Troubleshooting completed.