Hi Guys, Check light came on couple days back. Error Code Reads P0401 EGR Flow Insufficient. Some body was telling if we replace the Air Filter it will go away. I haven't changed the airfilter from last 5 months. Can you guys give me some advice on this, Appreciate your help Thx
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It's probably not your air filter, but have a look at it anyway and replace it if it's dirty.
Try looking at the Emission Control manual on camrymanuals.com (yours is a Gen 4 Camry). There will be a diagnostic procedure in there.
Sometimes all it takes is to clean the EGR valve.
There are quite a few threads about P0401 in the Gen 3&4 forum on toyotanation.com.
This problem (P4001) started in my car (2000 camry) two weeks back.
It seems like there are 5-6 reasons for this:
1) EGR valve bad (Do vacuum test at idle to verify this) 2) EGR vacuum modulator bad (Block port P and R and blow air thru port Q) 3) VSV (for EGR) bad. Difficult to locate this. Have to get under car for this. 4) Hoses or port clogged (In EGR valev or vacuum modulator or throttle body inlets) 5) Temp sensor bad (This is what the OBD uses to detect whether EGR operated after command to open it) And a couple of others reasons.
after command to open it)
An update.
I cleaned the 3 vacuum hose from EGR Vacuum modulator and 1 hose from EGR valve amd also the ports leading to throttle body Used a thin metal wire first and then compressed air.
And now check engine light (for P0401) no longer appears.
And to think of, the local mechanic wanted to replace the EGR valve (for $200 parts included). Somewhere, I had read that that is what most mechanics do for P0401. They take the easiest path of first replacing the EGR valve.
Diwa is right.
Check the EGR valve first by using a free loaner MityVac vacuum pump on the EGR valve itself. If the engine runs rough at idle when you pull vacuum then you know the valve is good.
Most of the problems come from carbon-plugged small vacuum ports/ hoses. Cleaning them should make things work most of the time. (This includes the small ports in the throttle body that send vacuum signals to the vacuum modulator)
Diwa is right.
Check the EGR valve first by using a free loaner MityVac vacuum pump on the EGR valve itself. If the engine runs rough at idle when you pull vacuum then you know the valve is good.
Most of the problems come from carbon-plugged small vacuum ports/ hoses. Cleaning them should make things work most of the time. (This includes the small ports in the throttle body that send vacuum signals to the vacuum modulator)
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