Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSMAZDA20086 S SPORT, 4D HATCHBACK, STANDARDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISON-BOARD DIAGNOSTIC [ENGINE CONTROL SYSTEM (AJ]DTC P0403 [AJ]DIAGNOSTIC PROCEDURE

2008 Mazda 6 s Sport, 4D Hatchback, Standard

Diagnostic procedure

2008 Mazda 6 s Sport, 4D Hatchback, StandardSECTION Diagnostic procedure

DTC P0403 [AJ] 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 on-line repair information availability. Is any 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	CLASSIFY INTERMITTENT CONCERN OR CONTINUOUS CONCERN Turn ignition switch to OFF then ON (Engine off). Is same DTC present?	Yes	Go to the next step.
3		No	Go to intermittent concern. (See INTERMITTENT CONCERN TROUBLESHOOTING [AJ] ).
4	INSPECT EGR VALVE CONNECTOR FOR POOR CONNECTION Turn the ignition switch off. Disconnect EGR valve 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 11.
4		No	Go to the next step.
5	INSPECT EGR VALVE POWER CIRCUIT FOR OPEN CIRCUIT Turn the ignition switch to the ON position. Measure voltage between following circuits: EGR valve terminal C and body ground EGR valve terminal D and body ground Is voltage B+ ?	Yes	Go to the next step.
5		No	Repair or replace harness for open circuit, then go to Step 11.
6	INSPECT EGR VALVE CONTROL CIRCUIT FOR SHORT TO GROUND Turn the ignition switch off. Check continuity between the following circuits: EGR valve terminal A and body ground EGR valve terminal B and body ground EGR valve terminal E and body ground EGR valve terminal F and body ground Is there continuity?	Yes	Repair or replace harness for short to ground, then go to Step 11.
6		No	Go to the next step.
7	INSPECT EGR VALVE Inspect EGR valve. (See EGR VALVE INSPECTION [AJ] ). Is there any malfunction?	Yes	Replace EGR valve, then go to Step 11. (See EGR VALVE REMOVAL/INSTALLATION [AJ] ).
7		No	Go to the next step.
8	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 11.
8		No	Go to the next step.
9	INSPECT EGR VALVE CONTROL CIRCUIT FOR OPEN CIRCUIT Turn the ignition switch off. Check continuity between the following circuits: EGR valve terminal A and PCM terminal 2R EGR valve terminal B and PCM terminal 2S EGR valve terminal E and PCM terminal 2Q EGR valve terminal F and PCM terminal 2O Is there continuity?	Yes	Go to the next step.
9		No	Repair or replace harness for open circuit, then go to Step 11.
10	INSPECT EGR VALVE CONTROL SENSOR CIRCUIT FOR SHORT TO POWER Turn ignition switch to ON (Engine off). Disconnect EGR valve connector. Measure voltage between the following terminal and body ground. EGR valve terminal A EGR valve terminal B EGR valve terminal E EGR valve terminal F Is voltage B+ ?	Yes	Repair or replace harness for short to power, then go to the next step.
10		No	Go to the next step.
11	VERIFY TROUBLESHOOTING OF DTC P0403 COMPLETED Make sure to reconnect all disconnected connectors. Clear DTC from PCM memory using M-MDS. Perform the KOEO or KOER SELF TEST using the M-MDS. (See KOEO/KOER SELF TEST [AJ] ). Is the PENDING CODE same DTC present?	Yes	Replace PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [AJ] ).
11		No	Go to the next step.
12	VERIFY AFTER REPAIR PROCEDURE Perform "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE [AJ] ). Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [AJ] ).
12		No	Troubleshooting completed.

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.