P0401 code questions

[BLRobertson]

I've been chasing a P0401 code on our 2000 Camry 2.2L 115 k for longer than I care to admit. All the suggested checks & cleanings(multiple times) have been done. All components are functioning, hoses good and the modulator was replaced due to the dark spot on the filter. I've checked vacuum readings while driving and Port R has little or no vacuum under any throttle positon Port Q flucuates from 0-15 and moves around at a steady RPM over 2000 rpm. Port P shows 0 to a max 2.5 and EGR port also shows 0-2.5. The EGR requres 3-3.5 inches to fully open. Do these numbers sound right? It seems I should be getting more vacuum through the modulator to fully open the EGR valve. What vacuum reading should I be seeing in a system that operates properly? Do I need to clean out the Throttle body better? I've got lots of patience but this has become very frustrating and I'm not ready or convinced I need to throw money at parts that appear to be working.

[csaxon]

http://www.tundrasolutions.com/forum...2-2l-2001-vsv/

Good threads.

[JohnGD]

Never throw money at parts before you had a chance to perform proper diagnostic procedures on them. This vacuum operated EGR design sucks (figuratively and literally ). But we'll see what we can do:

Plug the MityVac vacuum gauge (like one from the Autozone free loaner tool program) to the Ports E and R (one at a time) on the throttle body, as you open up the throttle to 2500-3000 rpms, what do you read on those ports?

If you don't read anything near full engine vacuum then you should clean those ports first on the throttle body. Only then do you proceed with testing other parts of the system.

At operating temp and 2500 RPMs, also try applying 15" in/HG to Both Port P and Port R on the modulator. How does the engine perform when you do this?

Edit: On second thought, you may not have a tee, so see if you pull 15" on just Port R of the modulator can you make the engine run a bit rough.

Originally Posted by BLRobertson

I've been chasing a P0401 code on our 2000 Camry 2.2L 115 k for longer than I care to admit. All the suggested checks & cleanings(multiple times) have been done. All components are functioning, hoses good and the modulator was replaced due to the dark spot on the filter. I've checked vacuum readings while driving and Port R has little or no vacuum under any throttle positon Port Q flucuates from 0-15 and moves around at a steady RPM over 2000 rpm. Port P shows 0 to a max 2.5 and EGR port also shows 0-2.5. The EGR requres 3-3.5 inches to fully open. Do these numbers sound right? It seems I should be getting more vacuum through the modulator to fully open the EGR valve. What vacuum reading should I be seeing in a system that operates properly? Do I need to clean out the Throttle body better? I've got lots of patience but this has become very frustrating and I'm not ready or convinced I need to throw money at parts that appear to be working.

[JohnGD]

BTW, we need to talk about ports on the modulator or ports on the throttle body. Toyota did a poor job naming these ports. (For example, port P connects to port E).

I think you may have a case of mistakenly routed hoses on the modulator.

So:

1. Do the throttle body port checks I talked about. See if you get the proper vacuum readings from them. Well, tell us what you read as you open the throttle from idle to about 2500 RPMs.

2. Which port on the modulator is connected to the VSV and then to the EGR valve?

3. What ports on the throttle body are connected to what ports on the modulator?

[sherbear123612]

ive got the same CODE right now and im about to replace the EGR TEMP SENSOR apparently everything with my egr system is working.... but the sensor is not..... the part is about 129.00 through my local parts house.

[Uncle Shadetree]

Originally Posted by sherbear123612

ive got the same CODE right now and im about to replace the EGR TEMP SENSOR apparently everything with my egr system is working.... but the sensor is not..... the part is about 129.00 through my local parts house.

Going through the same probs and feelin the pain. Can't pass emissions test! BTW...I just replaced my egr vsv and it wasn't the problem. Someone on this forum suggested taking off the right front wheel to get better access to it if you don't have a hoist, much appreciated that tip!

[ajkalian]

Here's some links to another guy's take on how to diagnose and fix the Toyota EGR problem. The first link is for the 4cyl, the second the 6cyl.

Hope this helps.

http://www.motor.com/magazine/pdfs/092009_04.pdf
http://www.motor.com/magazine/pdfs/112009_04.pdf

[hill8570]

Originally Posted by sherbear123612

ive got the same CODE right now and im about to replace the EGR TEMP SENSOR apparently everything with my egr system is working.... but the sensor is not..... the part is about 129.00 through my local parts house.

Did you actually test the sensor? Pot of boiling water and one of those cheap $4 Harbor Freight multimeters ($1.99 with coupon from the Sunday paper) and you've got a pretty good go-no-go test.

[sherbear123612]

Originally Posted by hill8570

Did you actually test the sensor? Pot of boiling water and one of those cheap $4 Harbor Freight multimeters ($1.99 with coupon from the Sunday paper) and you've got a pretty good go-no-go test.

yes! i had it tested at work. we have this program called ALL-DATA its what the mechanics use so i messed around on that for a while and found a whole walk through basicly to test and inspect the whole EGR SYSTEM.
then i bribed on of the guys with food lol
he got to the sensor part and found that the sensor wasnt working... he probed and tested it and its soon to getting replaced.

[sherbear123612]

Originally Posted by Uncle Shadetree

Going through the same probs and feelin the pain. Can't pass emissions test! BTW...I just replaced my egr vsv and it wasn't the problem. Someone on this forum suggested taking off the right front wheel to get better access to it if you don't have a hoist, much appreciated that tip!

i replaced the VSV a few years ago and another thing and last year replaced the vacume modulator... and now this year ill be doing the EGR temp sensor. and you shouldnt have to take the wheel off to get to stuff... all the EGR is right there with the intake.... and btw if you live in tx and live in an emissions county. check out air check texas they pay up to $600.00 in emissions repairs. as long as you qualify.

go to air check texas.com or google drive a clean machine you can find all the info

ok just to update since doing valve cover gaskets and intake gaskets along with cleaning egr ports in the intake manifold i no longer have an egr p0401 code i also replaced the EGR valve gasket on the lower side of the EGR valve it self...... also used B-12 in the gas and everything running AMAZING!

[BLRobertson]

I'll try to clarify my hose and port layout better and the readings I got this morning. Port R(fwd tube on throttle body aimed at modulator) connected to fwd port on L/H side of the modulator, I have 1 inch at 2500 RPM. Port P(aft tube on throttle body aimed at modulator) connected to aft port on L/H side of the modulator, I have 14 inches at 2500 RPM. Port Q(R/H side of modulator to VSV) I have 2-2.5 inches at 2500 RPM. There's a Port E on the throttle body and it is twice the size of R & P aimed outboard and I believe it's feeding the EVAP system. The throttle body is metal stamped with letters and there's a modulator placard so if R-R and P-P is what I'm looking for that's all good. So should I be getting about the same readings at R & P when operating properly? I'm going back to pull the throttle body and clean it good. I've been pumping B 12 down the port and see a steady stream but I've got some Deep Creep to try and see if it works any better. If I'm heading the wrong direction with this let me know. Sorry about the delay in responding, I can only get to these things on the weekends thanks for the patience.

[BLRobertson]

I've pulled the throttle body, sprayed and cleaned it. While removing the intake hose I noticed the smaller hose going to a black plastic box was torn and repaired it. Replaced all vacuum hoses between the throttle body and EGR valve. Verified hose routing per placard on hood and had 2 others double check the routing. Pulled VSV, tested and showed 38 ohms, not shorted to ground and operated properly with and w/o power. Opened modulator and checked filter-this unit is nearly new but thought I'd look anyway. Here's the vacuum readings. Readings taken with engine warm to operating temp.



RPM.......Port R.......Port P.......Port Q.......Port E.......EGR



Idle..........0..............0..............0..... .........21...........0



2500.........2.0...........14.0..........14.0..... .....21.5.......0



Driving

2500.........2.0...........14.0...........2.5..... ......n/a.......2.5



What affect was the torn hose having and is it some kind of resonator? Do these readings look funny? When I wasn't gettig any vacuum to the EGR at 2500 RPM I pulled and tested the VSV. After it bench tested OK I drove it with my gage teed into various ports and had vacuum to EGR valve but not enough to fully open the valve.Also what would account for the drop in vacuum at Port Q while driving. Let me know what else I should look for. Thanks.

[xtremexnyc]

Please provide the part # for the VSV. Thanks.

[xtremexnyc]

Replaced the VSV. Reset the codes. Now I will see if the code does come back. For any one that needs the part for the VSV it is 25860-74050. This is for a 2001 Camry but I am sure it can be used for other years.

Thanks

[fenixus]

BLRobertson, did you solve your problem ?

My '00 Solara SE i4 has a (NOT) funny problem with no vacuum at EGR valve at all. VSV and modulator are new, all hoses checked out, i'm at wits ends here. i don't understand why EGR valve is not getting any vacuum at 2,500rpm at warm engine. I see you had similar trouble.