Code P0401

Hi there

I been working on a 2002 toyota tacoma xtracab prerunner 2.7L. The check engine light went off and it shows code P0401 Insufficient Exhaust Gas Recirculation (EGR) Flow.

I took the intake manifold out and cleaned all the openings coming from the EGR valve, there was barely any carbon buld up. I also noticed the EGR Temperature sensor had some carbon so I cleaned it real good. I didn't replace the EGR valve hoping that cleaning the openings and EGR temperature sensor would fix the problem.

I put everything back together and drove a few miles. The check engine light went off once again.

I replaced the EGR Valve 1 hour ago and the check engine light went off. What am i missing? what else would you do? what am I missing?

Thanks in advance.

 

Double check all vacuum lines, especially the ones on top of the throttle body.
Try that before throwing parts at it.
There's a ton of posts on this code, check em out and save some time, $, and headaches

 

I been reading about a VSV (vacuum switching valve) failing on some cases. I been looking for one online but I'm guessing this tacoma has a different name for it. Anyone lnow them by a different name?

 

I thought the P0401 was the old loose gas cap code. No?

 

The Factory Service Manual (FSM) has a troubleshooting section on all codes. P0401 is on page DI-101. You can download it from the Sticky section at the top of the screen.

It shows the testing procedure for the VSV for EGR.

 

The vsv that fixed my P0401 was this one at a fraction of the price of OEM part, but made by the manufacturer that makes the OEM vsv.

$36 Aisin VST-001 Bulk Vacuum Switch Valve - Green

https://www.amazon.com/Aisin-VST-001-Vacuum-Switch-Valve/dp/B00NFJIF78
And its a few bucks less from when I bought it over the summer.

 

Unfortunately, as you found out, it's usually not the EGR valve itself that fails. It's usually the modulator or the vsv.

 

X2 ^^ Just be prepared to shred your knuckles installing it. Ha Ha.

 

Your first name reminded me I need to binge watch second season of Better call Saul one of these days. Lol

 

try purge solenoid.

 

Just remembered, you can also try cleaning off the EGR temp sensor. You may have already done that though.

 

OP claims he 'cleaned it real good'.

The temp sensor was my 0401 problem. At first, I cleaned it with a spray-on TB cleaner. The CEL went away for a week. Then I cleaned it with a knife (scraped off that black crud) about 3 years ago. No CEL since.

If the CEL ever comes back, I'll finally break down and get a new one.

 

I will do a through inspection, today after work. I hope it's just a hose. Been spending quite a bit of $$. I'm about to throw the towel.

 

Big fan. It's been kinda boring. I guess I'm used to the old Saul from Braking Bad, the funny Goodman.

 

My dad showed up when I was working on it and he used a emery cloth to clean it while I was putting the intake back in. I tried to clean it with throttle cleaner but the carbon was really in there. He did a decent job.

 

Cool man, you can test each of the components in the EGR system. The EGR valve itself can be tested for function while still on the engine. I believe the modulator should be removed to test, as well as the VSV. The steps to test these are in the FSM, I believe. Do you have access to a copy of the FSM or the digital version of the FSM?

 

Sadly I do not have the FSM. You got any idea where to find it?

 

I think there is a link to download the FSM in one of the threads in the sticky section. Or someone else might chime in with a link or copy.

 

Post #5. It's in the sticky section.

 

I checked it but the website it sends me to doesn't have them anymore.