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OBD-II Trouble Shooting Got a code reader? Find out what your GM car's Check Engine light is trying to tell you (and then turn Check Engine light off).

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Old 09-24-2009, 05:56 PM   #1
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Default P0401



PCM tests Exhaust Gas Recirculation (EGR) valve by
momentarily commanding valve on while monitoring engine MAP. PCM will
illuminate MIL and store DTC P0401 if expected increase is not seen
under certain conditions during deceleration.

You may notice drivability problems such as pinging (knock) when the engine is under load or the vehicle is at higher speeds.

  • The valve is not opening or closing
  • There is a blockage in the EGR (tube), most likely carbon buildup
  • The EGR valve is faulty
  • Damaged or cracked EGR tube causing a vacuum leak
Possible Solutions
  • Remove EGR valve and inspect
  • Clean out the EGR valve and/or tubing to remove carbon build up
  • Check to make sure EGR plug is clean and tight.
  • Check for vacuum leaks
  • Replace the EGR valve
Related EGR codes: P0403
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obd2, obdii, p0401, p401

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