1999 4Runner P0409 code

Hello,
I’m having this issue with solving a P0409 code. I’ve changed the spark plugs, the EGR valve & the vapor canister purge solenoid. However this still persists. The code only comes on when I start driving when the engine is cold. It does feel a little sluggish at first. If I let the engine warm up, it won’t trip the fault code.

Thoughts?

 

What engine? What transmission?

 

4 cylinder, automatic transmission

 

P0409 = Exhaust Gas Recirculation Sensor "A" Circuit
https://www.obd-codes.com/p0409

I don't know this engine but from a little research it seems that it's probably the sensor for the EGR is bad since you replaced the EGR. Have you replaced the EGR sensor?

 

Did a little hunting and found a guy who made a few videos on EGR valves. More info than anyone needs to know but if I were to guess, and your EGR is electronic like his in part 3, you still have a bad EGR that's reporting bad resistance to the ECU or bad wiring. Maybe someone else here has more experience.

https://www.youtube.com/watch?v=AVC8qBwQlRw
https://www.youtube.com/watch?v=z3ob7cqOtXY
https://www.youtube.com/watch?v=RQL7Wp7RaYc

 

Hello and thank you for this thorough reply. I must self disclose that I remembered the code number incorrectly, the correct fault code is P402 which also happens to be an EGR problem potentially.
Since I’ve already replaced the EGR valve and solenoid, I’m suspecting the ignition system. The check engine will not illuminate when I warm up the car before driving it.

thoughts?

thank you in advance!

 

P0402 = Exhaust Gas Recirculation “A” Flow Excessive Detected
The ECU is detecting excessive exhaust flow through the EGR.

Why would you think the ignition system is an issue? That makes no sense to me.

A search for 4Runners with that code, it seems the most common fix seems to be replacing all your vacuum lines to and from the EGR. Some good info here... There is an EGR switching valve that also fails.

 

Hello, thank you for your prompt response.

The reason I was suspecting the ignition system is because when I changed the spark plugs, the P402 code was not tripped as often and it started running better at idle than before. But maybe that was a separate non-related issue.

I have already changed the EGR switching valve and that didn't help. Perhaps I need to start taking a closer look at the vacuum hoses.

Thoughts?

Thanks!

 

Engines are air pumps. Running better means more air is moving through the engine, which means more circulating gases. I imagine that means more air through the EGR and this code trips faster because of it.

The computer is literally telling you which system is the issue...so while it's good to look at everything as a whole, I'd stay focused on the EGR system.

 

I never did locate the vacuum leak but the head gasket blew last week. Made it home the last bit on 2 cylinders. I’m suspecting a leaky head may have had a hand in this issue. Taking it all apart as we speak.