Searching for P0401 cause - 95 Tercel

[MacTerc]

Got a '95 Tercel, that seems to be running fine (getting 35mpg). But, cannot get rid of the CEL - keeps coming up with code P0401. Dealership said it was the EGR valve - ordered it and replaced it - code came back within a couple days. Taken it to a couple different shops, and they've done vacuum leak checks, can't find any. One mechanic removed every vacuum tube going to the EGR and blew each one clean, still nothing. I'm getting tempted to remove the light bulb behind the light - to get the wife off my back. Any ideas ?

[tercelsuperfast]

Ah yes, finally I can help someone with the same problem I had. I had that problem, I cleaned every vacuum, checked everything, it took me forever to figure it out.....

There is a metal line that runs from the EGR valve to the intake manifold....where it bolts to the intake manifold, that port gets clogged almost totally shut because of the PCV system dumping oil in it. Remove that line, and you'll also have to remove the throttle body to get to the port in the intake manifold...get some pipe cleaners and a screwdriver, anything you can get in there, I used an allen wrench, and ream the hole clean, and clean with some carb cleaner(2+2)...

More than likely that's the problem. I had checked the EGR valve, cleaned it, enlarged the hole of the EGR valve, cleaned the pipe, cleaned all vacuums, tested the vacuum switching valve, and the ciruit going to it, tested the vacuum modulator, and cleaned the port in the head to the EGR,...........all this before i figured it out. Also check out my tutorial on it...

http://board.tercelonline.com/viewthread.php?tid=19633

[idavid76]

Sorry guys, a little off topic. Can you tell me where the CEL is at in the instrument cluster. I just bought a 95 Tercel and when I first start the car it does NOT go on with all the other warning light that normally go on when the ignition switch is turned to the "ON" position. Is this normal, for the light NOT to go on when first started.

[jeffs94]

Originally Posted by idavid76

Sorry guys, a little off topic. Can you tell me where the CEL is at in the instrument cluster. I just bought a 95 Tercel and when I first start the car it does NOT go on with all the other warning light that normally go on when the ignition switch is turned to the "ON" position. Is this normal, for the light NOT to go on when first started.

The light should come on as part of the internal self test at start up....if its not , you may have a burnt bulb or a PCM problem(least likely though).......check the bulb.....and sometimes you can see whats on the face of the cluster by shining a flashlight directly at it, sometimes.....

[idavid76]

Thanks a lot Jeff, I will remove the cluster and check the bulbs. I just hope that someone didn't pull out the bulb just to get rid of the annoying light being on...and I just bought a car with a problem, although it runs like a champ.

[idavid76]

Jeff fixed light problem. All it was a burnt out bulb, CEL comes on at start up and quickly turns off. So at least I know car is OK. Thanks again!

[jsiegel5]

Thanks for the great info. My 1995 Tercel with 252k miles threw P0401. Lifting up on the EGR diaphragm caused no engine reaction at idle. I removed the metal pipe from the EGR output to the Intake Manifold. Pressue at the EGR output seemed good. Vacuum at the Intake Manifold was poor. I used some 12 gauge stranded copper wire to scrape inside the manifold. Strip the wire back about 1" and splay the ends a little. Insert the wire into the manifold and twist back and forth. I got a fair amount of carbon out doing this, and afterwards vacuum was noticeable improved. With the pipe reinstalled, lifting up on the diaphragm now makes the engine stumble, like it should.

Regards,
Jeff