LS Idle Air control valve

[lonestarlslover]

After doing some more looking at the wiring diagrams, fuse 110 (5A) and the one that powers your IAC is ALWAYS powered. Very strange. The other wire in your IAC connector is the ground which goes to the ECM for control. I still think this is fairly easy to diagnose with a little time and effort. Since it looks like the IAC is constantly powered, it has to have a ground to operate. From what I see, the ECM controls the ground to run the motor. So if it's constantly being activated, it is grounding somewhere. Let's take a look at a couple of things and see if we can't isolate where the ground is. The first thing I would do is remove the connector from the ECM. If your IAC quits being activated, then I would assume it's a safe bet you have a bad ECM. However, it is very rare for an ECM to go bad, so be prepared to start looking elsewhere. If disconnecting the ECM does NOT fix the problem, disconnect the harness connector at the IAC and run a 12V power supply (jumper wire) to the power side pin of the IAC. If the motor starts activating without a ground hooked up like that, then the short is in the IAC itself. If not, then the short is in the harness between the IAC and the ECM. That could be a real bitch to find. If that's the case, you could always run a new wire and splice and solder it in between the IAC motor and the proper pin on the ECM. This is pin #9 on connector C175C if it helps.

Stay with this and let us know what you find!

I'm a little bit ahead of you, at this point i have unpluged the IAC and it stops running, but that is both wires so it would, i need to fine a way to disconect the ground wire or run a hot wirs to the IAC , i see where your going. I'll stay in touch...... the beat goes on, lol thanks again for your help

 

[lonestarlslover]

IIRC the LS uses ground switching so this may explain the always hot. disconnecting the ground is a good idea as you stated that would indicate a short if the problem persisted.

Good job looking out for him 01LS8.

Is this ground switch in the ECM ? Thanks Again for your input.

 

[Quik LS]

hopes this helps:

 

[lonestarlslover]

hopes this helps:

Yes, this helps, Thank you. The PCM is behind the glove box right ? My hot lead is orange w/yellow w/ an inline 5A fuse. Brown going to PCM , The IAC is just for idleing correct ? And should not be working, or lets say be engaged at speed .

 

[Quik LS]

yep - up under the glove box in the upper corner of the passenger footwell.

the wiring is on the inside of the engine bay - you have to pull out the cabin air filter, and all the duct work to get to it.

 

[lonestarlslover]

yep - up under the glove box in the upper corner of the passenger footwell.

the wiring is on the inside of the engine bay - you have to pull out the cabin air filter, and all the duct work to get to it.

Well, that will be enjoyable :Bang ...... lol Thanks for your help

 

[lonestarlslover]

Well, that will be enjoyable :Bang ...... lol Thanks for your help

This is what i'm looking at under the hood. i see the green wire w/yellow, but it goes no further then this connection, brown wire goes in and out, but the green doesent, any ideas as to why ?

 

[Quik LS]

the diagram shows the green/yellow tapping into a slice (S125) and using the same green/yellow wire that run from the hydralic fan soleniod to the large fusebox connector (C140)

 

[lonestarlslover]

the diagram shows the green/yellow tapping into a slice (S125) and using the same green/yellow wire that run from the hydralic fan soleniod to the large fusebox connector (C140)

My question is : What is its purpose , the green wire, it splices in at that connector in the pic ? With the brown wire that goes to the PCM as a ground as i understand it. The green wire at that connection goes nowhere . So if it is spliced in at that point is it a ground as well ? Trying to cover all my bases here. :Bang

 

[lonestarlslover]

A Ford dealership could do the same diagnosis for $50. Autozone can give a you the computer error code for free.

Oh, sorry, I didnt see you there ........ I'm a bit of a "Do it yourselfer" ...... Grew up working on early model Mustang's and Bronco's, now in my retierment years it gives me something to do, but push come to shove i'll end up at the dealership. thanks for the help :wrench

 

[2001LS8Sport]

the diagram shows the green/yellow tapping into a slice (S125) and using the same green/yellow wire that run from the hydralic fan soleniod to the large fusebox connector (C140)

That should be for the early build Quik...he has the later build which uses the other circuit and doesn't tie into the fan solenoid. (it's powered by a 5A fuse # 110)

You are getting real close to having this worked out! Don't give up the ship now! You can reverse my proceedure somewhat and possibly save having to disconnect the ECM. Just hook your 12V jumper to the power side of the IAC and see if it activates. If not, then the IAC probably doesn't have an internal short. If it does, you're probably done and found the problem. If it doesn't, then take the time to disconnect the ECM and power the car and see if it activates or not. Again, if it does, then you have a short in the wiring to the ECM. If not, then the short is the ECM itself. By the way, the brown wire is the ground (return) to the ECM.

Hey guys...since I don't have the car here with me, can't you disconnect the ECM without pulling it out in these cars? Isn't the plug on the engine side of the firewall? Takes an 8 or 10mm socket? I can't remember for sure.

 

[Quik LS]

Hey guys...since I don't have the car here with me, can't you disconnect the ECM without pulling it out in these cars? Isn't the plug on the engine side of the firewall? Takes an 8 or 10mm socket? I can't remember for sure.[/QUOTE]

right - you can get at the PCM wiring without pulling out the ECM.

 

[lonestarlslover]

That should be for the early build Quik...he has the later build which uses the other circuit and doesn't tie into the fan solenoid. (it's powered by a 5A fuse # 110)

You are getting real close to having this worked out! Don't give up the ship now! You can reverse my proceedure somewhat and possibly save having to disconnect the ECM. Just hook your 12V jumper to the power side of the IAC and see if it activates. If not, then the IAC probably doesn't have an internal short. If it does, you're probably done and found the problem. If it doesn't, then take the time to disconnect the ECM and power the car and see if it activates or not. Again, if it does, then you have a short in the wiring to the ECM. If not, then the short is the ECM itself. By the way, the brown wire is the ground (return) to the ECM.

Hey guys...since I don't have the car here with me, can't you disconnect the ECM without pulling it out in these cars? Isn't the plug on the engine side of the firewall? Takes an 8 or 10mm socket? I can't remember for sure.

I'm pretty much to this point, i'v removed the glove box, the C/D player and i'm looking at a box that looks like its , oh 6" long and maybe a little over an inch thick mounted flat, i also see a smaler box next to the C/D player mount , and a fuse panel against the side wall i didnt know was there, i know you guys are asking how the hell i didnt know it was there ..... lol I'v had the car 2 years but seldom do i drive it, to the point where i'v only changed the oil twice, So its the bigger box that i'm looking for, Right ?
It sure is good to have guys like you around, thanks again.

 

[lonestarlslover]

Hey guys...since I don't have the car here with me, can't you disconnect the ECM without pulling it out in these cars? Isn't the plug on the engine side of the firewall? Takes an 8 or 10mm socket? I can't remember for sure.

right - you can get at the PCM wiring without pulling out the ECM.[/QUOTE]

Does anyone have a picture of the PCM or the ECM ? :soapbox:

 

[Quik LS]

right - it's that metal box - held in by a metal bracket that goes around the rear - held on with a bolt in each end.

 

[lonestarlslover]

right - it's that metal box - held in by a metal bracket that goes around the rear - held on with a bolt in each end.

Ok, Thanks....... but i dont see any wires, Does that box plug in to any thing, or will i see the wires when i pull it down after unbolting it ?

 

[Quik LS]

right - all the wiring is from the engine bay side - you will not be able remove it until you undo all the wiring from the other side.

 

[lonestarlslover]

right - all the wiring is from the engine bay side - you will not be able remove it until you undo all the wiring from the other side.

This may be going deeper then i want to go ..... lol

 

[lonestarlslover]

Heres something strange..... the car was running and it died, the key was still on and the IAC stoped running, key off it started again, any thoughts ?

 

[lonestarlslover]

right - all the wiring is from the engine bay side - you will not be able remove it until you undo all the wiring from the other side.

Any ideas on how to get to the wires on the motor side of the firewall ?

 

[Quik LS]

- open the hood
- remove the push pins from the passenger side cowel cover, remove the cowel cover
- remove the cabin aif filter
- remove the cabin filter duct work by removing the 4 bolts
- remove the rest of the plastic sheilding by removing the 4 bolts
- the PCM front end is sticking through the firewall under all that

 

[2001LS8Sport]

There you go! Unbolt the connectors and your ECM is disconnected and you can finish your diagnosis. You didn't even have to undo a single item inside the car! If you find the IAC still activates with the ECM disconnected, you have a wiring short to ground on the wire to the ECM. Other than it would make me nervous as to where it is and what else MAY be involved, I would just solder and splice a new wire in and see how that works. But before you do, take a good look at the harnesses and see if you can locate a possible trouble spot that you could repair. You might look in the area of previous repairs and see if someone clamped a wire under something. Oh yea...never a better time to change your cabin air filter!!

 

[lonestarlslover]

- open the hood
- remove the push pins from the passenger side cowel cover, remove the cowel cover
- remove the cabin aif filter
- remove the cabin filter duct work by removing the 4 bolts
- remove the rest of the plastic sheilding by removing the 4 bolts
- the PCM front end is sticking through the firewall under all that

Thank you so very much !!! this is a great help ! :invasion:

 

[lonestarlslover]

There you go! Unbolt the connectors and your ECM is disconnected and you can finish your diagnosis. You didn't even have to undo a single item inside the car! If you find the IAC still activates with the ECM disconnected, you have a wiring short to ground on the wire to the ECM. Other than it would make me nervous as to where it is and what else MAY be involved, I would just solder and splice a new wire in and see how that works. But before you do, take a good look at the harnesses and see if you can locate a possible trouble spot that you could repair. You might look in the area of previous repairs and see if someone clamped a wire under something. Oh yea...never a better time to change your cabin air filter!!

Well ...... it's a little late for "NOT" unbolting every thing on the inside, but it was a good experance ..... lol ...... thanks for your help again :bash:

 

[lonestarlslover]

- open the hood
- remove the push pins from the passenger side cowel cover, remove the cowel cover
- remove the cabin aif filter
- remove the cabin filter duct work by removing the 4 bolts
- remove the rest of the plastic sheilding by removing the 4 bolts
- the PCM front end is sticking through the firewall under all that

All is unpluged.....and it stoped, this cant be a good sign :Bang