Car Questions
RepairPal is your advocate for car care advice and guidance


(1996 Toyota Corolla)
in Greenville, NY on March 20, 2011
I live in the Northeast, several months ago my MIL lamp posted a P0401 code “EGR Insufficient Air Flow” The following parts were tested and replaced where necessary: VSV for ERG, EGR Vacuum Modulator, and Vacuum Hoses. The passageways for the EGR valve were also checked for carbon buildup but it was clear. The EGR valve was OK.

The MIL Lamp was reset, however after driving approximately 30 miles the MIL lamp tripped another P0104 code. A qualified technician checked the system again but to date no reason could be found to trip the code.

Since nothing could be found I was wondering if this might be a possibility, could a cold running engine cause the MIL lamp to post a P0401 code. I noticed that this past winter with extremely cold weather that my engine was running below the normal temperature, around 160 degrees, since coolant temperature plays a part in determining EGR function I was wondering if a faulty thermostat or coolant temp sensor would cause the EGR system to not work properly? It’s the only other thing I could think of as a remote possibility. Before I change the thermostat and or Temp sensor I wanted to get your opinion?

Any input would be appreciated.

Thank you,

Displaying 1 answers & 0 comments
Popular Answer
on March 21, 2011
I think you need a new thermostat if the engine doesn't warm up properly. It's very important to run the engine hot enough. I think your engine takes a 192F thermostat, but check on that. It could affect the EGR and possibly set a diagnostic code for EGR.
If you want to find a specialist, here's a directory link for you:
RepairPal estimates are guaranteed at over 2,000 quality certified locations nationwide. Learn more

Similar Questions

View answers to similar questions from RepairPal's community of auto experts and enthusiasts.
This engine check sign cone mostly 3 week I calculated and all tym dealerships says ECM code . This car has onlt 3300...
Didn't find what you were looking for?