P0401 : EGR Flow Insufficient on 1996 Toyota Corolla

Hi Folks

Any suggestions for P0401 EGR Flow Insufficient for 1996 Toyota Corolla?

Tks,
bonnie*

Hi,

I am getting the same code. Is it hard to replace the EGR Valve?

on what kind of car? A toyota?

yes, a 96 toyota corrola 1.6litre
if I get one of the HAyes manuals -- will it show pictures of where it is and how to replace this device?

maybe, I'd recommend a subscription to http://www.alldata.com, close to the same price as the Haynes manual and the quality isn't even comparable, That's not a paid endorsement or anything just speaking from lots of experience

on EGR codes, we recommend replacing the EGR, vacuum modulator and VSV (if equipped) and cleaning out the carbon buildup to the intake from the EGR valve. if you want to test the EGR valve, just get a Mighty Vac, apply vaccuum and see if the car stumbles and/or dies when applied. Check the VSV, just put 12VDC to the VSV and blow through a hose. If you can blow through it-good. And when you take off the 12V, you shouldn't be able to blow anything through it. BUT EGR valves and VSV's DO intermittantly get stuck. So to be safe, we recommend repalceing all 3 and cleaning out the passageway.

thanks for the replies

keep us updated on how it turns out!

I am working on 97 Corolla right now and its getting P0401 code so i checked Solenoid VSV (it' GOOD), Checked EGR (its GOOD and cleaned it), Took out MODULATOR and cleaned all the ports (everything looked good) only thing i noticed is that port "P" on MODULATOR is a dead end i don't think it's clogged because i soaked it in brake cleaner and i used compressor to blow thru nothing worked. But the line that goes off Throttle Body "E" or maybe it's "P" and goes to "P" on VSV got vacuum when the car is running so i found that wired. Also port on Throttle Body "R" is not getting any vacuum or doesn't doesn't blow thru so it's like clogged or something tried to clean it by opening TB and spraying brake cleaner and then using Paper clip to push it in but no results. That "R" port goes from TB to MODULATOR "R" port. So i am a little confused because it seem like MODULATOR not getting any Vacuum since "P" on MODULATOR is closed shut and "R" port on TB is blocked. I don't think they both got so clogged up that i can't clean them out. This actually makes this car Federal or something because EGR is not activated ever. But i still get the P0401 code and i know the car is CA.

So what you guys think of this deal? I also think it could be MAP sensor, because that's what Mitchell telling me to look for after i checked all those parts. Any ideas on this? I really need some input on this situation, i need to get this car SMOGED so i can sell it (already got deposit).

I drew a diagram of EGR and VSV and EGR Vacuum Modulator since my scanner is not working and i can't upload the Vacuum diagram of EGR System.

All of your input will be appreciated.

so does the car stall when vaccum is applied to the egr circuit?

Yes, car dies when i apply vacuum to EGR. I only applied vacuum to EGR diaphragm and not to Modulator. Do you think i should apply vacuum to EGR Modulator and see what happens. Which port i should apply it to? port "R" or "P"???

I think you change the vsv first!

I have already changed VSV and i know both are good. I also got another 97 Corolla and i used VSV from that car to see if there any difference but none.

Well i just figured out the problem it was EGR Modulator, i took it off the good car that got NO CE light and it passed smog. Put it on the car that keep throwing P0401 code and drove it for 45 miles. No codes came on. Used my scanner to see if all the monitors were ready for smog. Suprizingly everything was ready except Catalytic Converter, but it's only one thing so i knew it should be OK with OBDII reader from smog machine. Took it to SMOG check 20 min later i got my SMOG papers and it all passed.

So it end up being EGR Modulator after all. Allied Auto Parts sell them for $92

but at Rockauto.com they have them for $47.79, best price online:

http://www.rockauto.com/catalog/x,carco ... rtGroup,19

Thanks for your help.

You're lucky to have another car lying around to yank parts from!

Recently went through this problem on three different Toyota products (97 Lexus LX-450, 97 camry, and a 96 Land Cruiser). In each case, the problem was the EGR modulator valve (labeled on top with letters P,Q,R) on top.

The easy check for this valve is to disconnect the 1/4" hose from the bottom of this sensor. If you can't hold a vacuum on this port to the valve (it is to a sealed diaphram inside the valve), the valve is bad. At our shop, we had several of these lying around from different Toyotas, and about 1/2 were bad.

If you had saved your old valve, I'll bet you would have found that it failed this simple test.