DTC P0401

On my 94 V6 XLE Camry a DTC "P0401 Exhaust Gas Recirculation Flow Insufficient Detected" triggered as I deccelerated then accelerated on an inclined highway. Note that this event did not trigger while idle running or during other driving conditions. I've removed EGR valve and tested, it holds vaccume but valve leaks due to carbon deposits, I've also removed and tested EGR vacuum modulator, it holds vacume and seems good.

I've extracted following feeze frame data using a scan tool.

Freeze Frame Data

------------------ Fuel System 1: Closed Loop Fuel System 2: Closed Loop Load Value: 47.4% Coolant Temp: 176 F Short Term Fuel Trim 1: 0.8% Long Term Fuel Trim 1: 0.0% Short Term Fuel Trim 2: 0.8% Long Term Fuel Trim 2: 3.9% Engine RPM: 2283 RPM Vehicle Speed: 65 MPH Intake Air Temp: 41 F

If P0401 event is a symptom what could be the problem?

Thanks, IceMan

Reply to
IceMan
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Make sure the egr valve is opening properly, if it is all carboned up it may need to be replaced. Also make sure that the vsv is operating properly and sending vacuum at the proper time. Btw it will only set egr codes when cruising on the highway because thats the only time the egr operates.

Reply to
JonS999

Looks rather plain to me. The key word is "flow." The valve is not operating physically or the flow thru the normally operating valve is restricted (clogged delivery passage) severely.

Reply to
Philip®

properly and

VSV = Vacuum Solenoid Valve

For those of you who didn't know. ;-)

Reply to
Philip®

Thanks, I've already checked EGR valve and EGR Vacuum Modulator so my next step is to check VSV and EGR pipe to the EGR valve and the exhaust system.

Reply to
IceMan

Clean the EGR port at the throttle body, its plugged. Remove the valve from the intake, dig out all the carbon. Remove the throttle body to scoop out the chunks that break off inside. Its chocked full I bet. Seen this a few times myself.

Reply to
MDT Tech®

The modulator valve is no longer working that cause PO401. I had mine just like that I changed the modulator cost me $76.00 (at dealer) after replacing it, you need to reset the computer by pulling the EFI fuse. Now working great no more Check Engine light.

Reply to
skosasih

Carbon deposits existed inside Air Intake Chamber (just after Throttle body) where EGR port exists, also Throttle Body had varnish inside. Ports R & E where clean.

Did procedure recommended by Philip to test EGR pipe to EGR valve and the exhaust system, it was clean.

I hope this is all it was for P0401 otherwise I suspect it to be intermittent, a VSV or EGR gas temp. sensor will be next.

Thanks, IceMan.

Reply to
IceMan

Just curious, you mentioned carbon deposits. Where does the carbon deposits come from? The Air Intake Chamber is before the combustion process which is what creates the carbon.

Reply to
Jack

The deposits come from the PCV system and from the EGR system. Blow-by from the crank case is sucked into the intake tract via the PCV system so that any unburned hydrocarbons can be burned. The EGR system introduces exhaust gases into the intake tract. The exhaust gasses are an inert gas and help fill the combustion chamber without upsetting the fuel/oxidizer ratio. This helps lower the peak combustion chamber temperature which reduces NOx formation and pre ignition.

Ed

Reply to
C. E. White

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