P401 Insufficient EGR Flow detected on 1999 Camry 4cyl - Toyota Nation Forum : Toyota Car and Truck Forums

steppinthrax · 07-03-2009, 10:43 AM

I have a 1999 toyota camry. Yesturday i got a Check light on my dash. took it in to autozone they pulled a P401 Insufficient egr flow. He told me not to replace the egr valve because it could be clogged or something. I just pulled the entire egr valve off my intake manifold and removed the modulator. The egr valve appears to be working fine. I can apply a vac and the diaphragm goes up. There is no carbon buildup to a point where it dosen't work. I pulled off the modulator as well. WHAT ELSE DO I NEED TO CHECK? Also what other components can cause a p401. The tube going down from the egr seems to be fine as well. How do I check the modulator.

I was reading online and it appers the modulator gets bad often??

***toyomoho*** · 07-03-2009, 02:50 PM

Suggest you visit the AutoZone website's vehicle repair guide section on this car. The site should have info on how the system works and troubleshooting.

Did you also check the steel tube connected to the valve for plugging and the VSV valve?

msrdude · 07-03-2009, 05:35 PM

Try testing the modulator. Apply vacuum to the bottom port of the modulator and if it does not hold vacuum, then your modulator needs to be replaced.
It could also be the VSV, vacuum switching valve or your manifold or throttle body is clogged.

grandelatte · 07-03-2009, 06:23 PM

I had the same code. (Every car and every situation is different, but) I changed the VSV and the problem is fixed.

kmr16442 · 07-03-2009, 06:39 PM

Open the top of the modulator and pull out the filter media. If it has a round black spot the modulator is probably toast.

05DCLB · 07-03-2009, 07:26 PM

The EGR vacuum switching valve is most common problem, is on back side of engine bolted to back of cylinder head, has 2 hoses and 1 elec connector.

fastss · 07-04-2009, 03:06 AM

check all vacuum lines for cracks in them. Also, remove a hose from the egr and put your finger over it.. if idle stays the same, it's clogged.

steppinthrax · 07-04-2009, 01:30 PM

Quote:

Originally Posted by kmr16442

Open the top of the modulator and pull out the filter media. If it has a round black spot the modulator is probably toast.

UPDATE

I removed the modulator and EGR valve. I cleaned them out. I pulled hte cap off the modulator. I noticed a black spot on the modulator where the hole meets the filter. I put them back and bolted everything up. I pulled the battery cable and put it back. The light hasen't came on since. I've been grocery shopping etc. I spent around 5 miles or so and the light hasen't came on. IDK.... Also what chemical should I use to remove build up carbon. seems the brakcleaner I was using withich usually is good at grease dosen't work well on carbon.

I also notice there wasen't much in there I mean it wasen't really dirty. I didn't check the VSV nor the tube that goes from underneath the engine to the EGR valve.

jakie018 · 07-04-2009, 03:42 PM

hi
i had the same problem and i clean the egr valve and change the egr modulator and then took the bettery terminal out. the light went out but after driving about 400 miles and guess what... light came back!

so my point is that you need to check your vsv valve which only accessible from under the engine threw right wheel..which very common to go bad on a camry (at least according a lot of thread on this site) can be check with the multimeter for resistance (which should be in the specification) anyways, if you need pic for where vsv located....i don't have a 99 Camry but do have for 96 Camry so let me know

forgot to mession one thing clean ur egr valve with either sea-foam deep creep (expensive ) or any carbon cleaner ....and if u do find out that vsv is bad i got mine from murrays website part#EGR287 with LLT warranty (cost 65.99+ shipping)

Agrippa · 07-04-2009, 05:50 PM

I had the same problem. I replaced the VSV on the back of the block which was a real pain to get to. Nothing.

Then I replaced the Vacuum modulator and that did the trick.

Chris Crash · 07-05-2009, 01:04 AM

I had the same problem. Originally I pulled the EGR off and cleaned it. That worked for a week or so.

Then the light came back on. I replaced the VSV and that fixed it just fine.

If I remember correctly it was around $80 at the dealer. Don't waste your time or money with VSV's from anywhere BUT the dealer.

Doc · 07-09-2009, 06:49 PM

Hey Everyone,

I've got a similar problem on a 2000 Camry LE 2.2 L 4 Cylinder. Following everyone's advice, I replaced both the EGR VSV and the EGR Modulator. However, I'm still getting the P04/01 code.....does this pretty much narrow it down to the EGR valve itself? Any help would be much appreciated!

Gibson99 · 07-14-2009, 12:22 PM

one thing nobody else mentioned is the EGR temperature probe. i don't know about the 4cyl's, but in the v6, it's a probe that screws into the side of the egr valve. it's how it knows exhaust gas is actually flowing or not. if this temp sensor is bad, has a bad connection, or something like that, then it will throw the EGR insufficient code. i learned about this little guy while doing my s/c in my 95...

anodyne · 07-14-2009, 09:32 PM

Can this problem be related to fuel? Specifically, ethanol that is now being added to gasoline?

Gibson99 · 07-14-2009, 10:17 PM

no, you would get misfire, lean, or rich codes from ethanol because it lowers the octane rating of the fuel. octane and knock have no effect on the egr system. and even then you'd have to run pure E85 instead of regular gas (which only has 10% ethanol, not 85%) to cause problems.