Well....I thought this booger was straightened out, but today he got all these codes.

0505 is for the IAC, 0110 is for the IAT sensor, and 0120 is for the TPS. First of all, there's like a 1 in 1 million chance that all three sensors went bad at the same time, and second....I tested the IAC when I cleaned it, and it tested just fine. Which really makes me think that something else is causing all this stuff to act up.

Any idea's on where to start troubleshooting? The truck starts, runs and drives great. You'd never know anything was wrong if the CEL wasn't on. It's a 99 Limited 3.4 Auto 4x4. 138k miles.

 

You have a Scangauge correct? Use it to be able to tell if the TPS is fine or out of whack.

Did you use silicone when putting the IAC back together?

I don't even know where the IAT sensor is? Find the FSM link and it should give you the ability to test the TPS and IAC with a DVM....

 

Yep, I'll check the TPS with the scangauge and make sure it seems like it's reading something close to what it should be.

Yep, used silicone on the IAC. Siliconed the joint between the IAC body and the plug, and siliconed the screw heads.


After doing a little research...I think his O2 sensor might be bad. I'm not sure if he has a Cali-spec truck or not, but since he only throws the CEL when it's cold, I wonder if the heating element went out on the O2, and it reads wacky until everything gets hot.

 

Quicksilver,

I cannot remember and did not bookmark the post concerning where one member siliconed his IAC and somehow that screwed with the plunger. When I cleaned mine out after a valve cover gasket replacement, I just used a new gasket and have been OK so far. I think the OP just used too much silicone.

If the O2's are original, I'd replace them. Also, for s#^ts and giggles, clean the MAF.

Let us know what you find.

 

I actually cleaned the MAF when I was doing the IAC and had the intake all apart. It was pretty dirty. I just realized though: I didn't pull the negative cable on the battery to reset the ECU. I wonder if the MAF going from really dirty to completely clean is messing with the computer since it didn't get reset.

And I will pull the IAC apart again and see if got too much silly string, I mean silicone, in there. The screw heads are easy to not mess up, but I did try to put a complete ring around the plastic plug piece, and it has a tight spot where the seal joint is pretty close to the plunger and magnet.

And of course, the O2's are still highly suspect, especially the upstream.

 

reset the ecu and drive... Don't get upset but um.. did you plug everything back in? maybe have the key on to listen to some tunes while you had things apart?

 

check grounds, see if you can get a wiring diagram, usually sensors have a common ground that they share either through the pcm or spliced into a single ground wire. usually when several things go bad its a ground or a fuse, and those are all on the ecm power fuse so probably a ground... either loose, corroded or broken off or otherwise unattached. sometimes when a ground goes bad sensors have a way of finding a ground through another sensor that scews things up too. anyway im starting to ramble, hope this helps