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 DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 589 (ON-BOARD DIAGNOSTIC [ENGINE CONTROL SYSTEM L3 WITH TC])DTC P0403NOTES

2008 Mazda 6 s Sport, 4D Hatchback, Standard

DTC P0403: Notes

2008 Mazda 6 s Sport, 4D Hatchback, StandardSECTION Notes

WARNING: This page is about a different car, the 2007 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0403 DETECTION CONDITION AND POSSIBLE CAUSES

DTC P0403

EGR valve (stepper motor) circuit malfunction

DETECTION CONDITION

PCM monitors the input voltage from the EGR valve. If the voltage remain low or high, the PCM determines that the EGR valve circuit has a malfunction.

Diagnostic support note

This is a continuous monitor. (CCM)
MIL illuminates if the PCM detects above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
PENDING CODE is available if the PCM detects the above malfunction condition during first drive cycle.
FREEZE FRAME DATA is not available.
DTCs are not stored in the PCM memory.

POSSIBLE CAUSE

EGR valve malfunction
Connector or terminal malfunction
Short to the power supply in the wiring harness between EGR valve terminal E and PCM terminal 4D
Short to the power supply in the wiring harness between EGR valve terminal A and PCM terminal 4G
Short to the power supply in the wiring harness between EGR valve terminal B and PCM terminal 4J
Short to the power supply in the wiring harness between EGR valve terminal F and PCM terminal 4M
Short to ground circuit in wiring harness between EGR valve terminal E and PCM terminal 4D
Short to ground circuit in wiring harness between EGR valve terminal A and PCM terminal 4G
Short to ground circuit in wiring harness between EGR valve terminal B and PCM terminal 4J
Short to ground circuit in wiring harness between EGR valve terminal F and PCM terminal 4M
Open circuit in the wiring harness between EGR valve terminal E and PCM terminal 4D
Open circuit in the wiring harness between EGR valve terminal A and PCM terminal 4G
Open circuit in the wiring harness between EGR valve terminal B and PCM terminal 4J
Open circuit in the wiring harness between EGR valve terminal F and PCM terminal 4M
Open circuit in the wiring harness between main relay terminal C and EGR valve terminal C
Open circuit in the wiring harness between main relay terminal C and EGR valve terminal D
PCM malfunction

Courtesy of MAZDA MOTORS CORP.

RENDER: 1.0x

NO RELATED

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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.