P0401

Description
EGR SYSTEM INSUFFICIENT FLOW

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

Causes

• 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