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GM-Frank, ASE Master Certified
Category: Car
Satisfied Customers: 431
Experience:  37 Years Automotive Diagnosis & Repair. Experience with all makes and models..
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what is the fix when the diagnostic troublle code reads PO403

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Submitted: 8 years ago.
Category: Car
Expert:  GM-Frank replied 8 years ago.



The P0403 code represents a problem with the Exhaust Gas Recirculation Solenoid or circuit.

Below is the chart that explians and directs us to where the problem may exist.


Since there are a number of components or wires that can be at fault for this code,I feel it is not going to be something that we should attempt to diagnose via long distance. You may wish to check the basic wiring and vacuum supply to the solenoid, but if you find that the ECM is at fault, you will want to have this type of problem backed up by a good part and labor warranty.

Most solenoids need about 20 ohms or slightly higher resistance on the primary winding circuits to function correctly.



  1. Using the VACUUM HOSE ROUTING as a guide, check to be sure that the vacuum hoses are correctly connected.
  2. Check the connection condition of the vacuum hoses, (removed, loose, etc.) and check to be sure that there are no bends or damage.

Be sure to clear any trouble codes after you have made any repairs to the system.

Below is a technical service bulletin I have located on your vehicle, It may or may not be related to your current problem. I simply wanted you to have it.

TSB Revision: TSB-06-13-012
DATE: September, 2006
MODEL: See below




This bulletin contains additional troubleshooting procedures for the vacuum controlled EGR system on the affected vehicles.


Write the TSB revision number of this bulletin in the "TSB Revision" box at the bottom of the affected service manual pages.

1995-1996 Mirage 1.5L and 1.8L (California emissions only)
1996 Mirage 1.5L and 1.8L (Federal emissions only)
1997-2002 Mirage 1.5L and 1.8L
2003-2006 Lancer 2.0L
2003-2006 Lancer Evolution
2003 Outlander
1996 Galant 2.4L
1997-1998 Galant 2.4L (Federal emissions only)
1999-2003 Galant 2.4L and 3.0L
1995-1999 Eclipse/Eclipse Spyder 420A and 2.0L Turbo
1996-1999 Eclipse/Eclipse Spyder 2.4L
2000-2005 Eclipse/Eclipse Spyder 2.4L and 3.0L
1996-1999 3000GT 3.0L
1996 Diamante 3.0L
1997-2004 Diamante 3.5L
1996 Montero 3.0L 12 valve
1996 Montero 3.0L 24 valve (Federal emissions only)
1996 Montero 3.5L
1997-2000 Montero 3.5L (Federal emissions only)
2001-2002 Montero 3.5L
1997-1999 Montero Sport 2.4L (Federal emissions only)
1997-1998 Montero Sport 3.0L (Federal emissions only)
1999-2003 Montero Sport 3.0L
1999-2004 Montero Sport 3.5L
1996 Truck 2.4L
1995 Expo/Expo LRV 1.8L and 2.4L (California emissions only)
1996 Expo/Expo LRV 1.8L and 2.4L (Federal emissions only)


The above information is all I have for your Code P0403. I hope this help you determine your course of action.

Have a Great Day


GM-Frank and other Car Specialists are ready to help you
Customer: replied 8 years ago.
I forgot to tell you that I was also getting a code PO 431. After I replaced the cat. converter and the dealer replaced two O2 sensors the PO 431 code went away. IT now came back with PO 403 cdde.
Expert:  GM-Frank replied 8 years ago.


Hello againCustomer

Thanks for the accept and the bonus, Let me look at the P0431.

The P0403 is most likely not related to the P0431, but here's the info I have.

According to my diagnostic charts, there are about 3 possibilities. Catalytic converter, Rear Heated O2 Sensor or PCM failure.





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