I've seen all the threads about the CEL and was wondering why you all are having such problems and then I get the dreaded CEL.

This is the situation - I changed my clutch master and knocked off a vacuum hose to the vapor pressure sensor on the evap canister. After about 100 miles, the code came on and prompted me to check the canister and I reconnected the vacuum hose.

Later, as the code persisted, I read the code and to my surprise it came back as the "lean bank 1" code when I was expecting something about the evap canister. I then took the consensus forum recommendation and cleaned the MAF and cleared the code. After several short trips, I re-checked for trouble and I'm getting the "yellow" indication for a soft code.

Will it take longer for the system to go back to green or is the problem still there?

 

If you cleared the code, then the code is clear. If it comes back, then the ECU is reporting the problem again. When you read it, and saw it "yellow", it means that the ECU hasn't seen the problem enough to pop the lamp, but it's counting.

{wow that sounds confusing!}

Each code is different, but some (like this one) require the problem condition to show itself a number of times (3, I think) before the CEL pops. That's what your reader is showing as a "yellow".

It may clear... If you want to help it along, pull the EFI fuse or the neg battery cable for a bit to reset the ECU (or just clear the code with your reader) then keep an eye on it for a while.

 

got that code.

step 1. remove maf

step 2. get electronic contact cleaner and blast away at the bulb and the 2 lil threads,

step 3. get your cotton swabs and clean the bulb and very very very gently nudge and twist with the swab on the 2 lil threads.

step 4. clean with 91% isopropyl alchohol

step 5. let it dry

step 6. apply electrical grease on the contacts of the connector and plug it in.

step 7. remove neg battery terminal

step 8 reconnect neg batery terminal

step 9. fire it up! all good now = )

 

It is counting when you get a yellow like that. It takes 3 "trips" for the ECU to throw the CEL at you. I'd just pull the negative terminal and then drive it until the CEL appears again. If you get another P0171 then I'd strongly suggest just buying a new one rather than trying to clean it again (on 99-02 4runners the MAFs are cheap compared to a 96-98).

 

From my experience:

I got the P0171 code along with a P0133 and P0130. So I knew my problems were a bad O2 sensor (front).

Others that have had just the P0171 cleaned or replaced the MAF with success.