You could have checked the IAC motor by disconnecting the IAC connector and trying to reset the P0505 code. If it resets, the IAC motor is bad. If it doesn't reset, there is a wiring or PCM problem. I will check the wiring diagram for grounds and let you know. Does the engine run? The fuel indication also comes from the PCM.

 

The four wires on the IAC connector go direct to the PCM. I would check the wire bundle for chaving and clean the connectors on the PCM. If no help, measure the continuity of the four wires between IAC connector and PCM connector. I can send you the wiring lateron when im at home as refefence for the measurements. If this all measures ok, i would expect the PCM.

 

It runs fine. Just the issue with the persistent code not staying cleared and fuel gauge. Thanks for the reply I'll check the wires over the week end.

 

The PCM is the second one, fuel gauge was the same on the first one [not working].

 

Here is the wiring diagram for measuring the IAC motor wires. Besides measuring continuity, i would also measure each wire to ground, to be sure that no wire insulation is damaged. (both connector C1 on PCM and connector of IAC motor should be disconnected for this)
The fuel gauge problem could be separated from the IAC problem. It can easily be an open wire. Here also attached the wiring for the fuel qty sensing.

 

Thanks Frank, Hopefully get to it this week end. Fingers are crossed.

 

Ok, let us know what you find.

 

Did a chk. on the wires on the PCM and found one bad, replaced it and cleared the code. It stays clear for three to four start ups but returns. Not sure it the computer needs time to recognize the fix. Did take it down the road and it did stay cleared. I'll do that several times and see if it stays clear. Seems to have a very high idle now, I'll have to check into that. So thanks for the wiring diagram Frango100. Still not sure but still hopeful it's fixed.

 

What happened to the wire, no continuity or shorted to ground? Was it a wire from the IAC stepper motor? Normal idle is around 650 rpm. If its a lot higher, then there is (still) a problem. Did you disconnect the battery during/after the wire change? If battery is disconnected, the PCM looses the IAC stepper motor settings and after connecting the battery again, the stepper motor will be moved to both end stops, so that the PCM will learn these positions again. It still will take a few starts for the PCM to know the right stepper motor position for the start.

 

Thanks for the reply Frank. Lost continuity in yl/bk wire from idle air control motor to pcu, spliced in new wire, seems fine now. I think my son did disconnect the battery at his house. He brought it here for dad to fix for fathers day. Lucky me. Just hoping to get it to pass emissions. Again Frank thanks for your help.

 

What rpm does it idle now? If only the idle is high, but no fault code set, then i would disconnect the battery for some minutes and try again. When the P0505 returns, then there is still a problem with one of the IAC wires or connectors.

 

Disconnected the battery and the idle seems fine now but still have the 505 chk engine code. It'll have to wait until the weekend to chk further but we'll get it. Did a wiggle test on all the connecters but it didn't indicate a issue. Thought perhaps when the new pcm was installed it may have had the wiring connecters installed in the wrong location on the pcm but appear to be the same as my wives GC so I guess not. Again thanks for the help. Bruce

 

Still trying too reason out the problem. Still have the 505 code, installed new grounds on pins 31, 32 of the Computer [C1], no luck still have the code. All the connecters have been cleaned with contact cleaner over and over. Now the engine has been changed by the previous owner, one thought is there some one who can tell by the vin # what engine the computer is for. if by chance the car had a 4.0 six and they put in a v8. Wouldn't the computer be programed for the six and keep throwing the 505 code because of the 4.7 in it. Just a thought. He never should have bought it. I did have to put in a engine wiring harness out of my wifes totaled GC. The previous owner said there was a issue with the old one. No codes on the other car ever that the harness cam from.

 

A PCM from the 4.0 will for sure not work on the 4.7, it will simply not even start, if the connectors would even fit.

 

Besides measuring the wires from the IAC to the PCM for continuity, you also measured them to ground? Because the problem is intermittent, i suspect a bad connection somewhere or a shaved wire which touches some metal part.

 

I have the same problem. Checked for air hose leakage, replaced IAC, and the PCM. The idle was at 2000 RPM constant. P0505 code after check engine light came on. 2001 4.7 V8. Idle went down after PCM was installed but started to rise a day later. Check engine came on and the code was back.

 

The harness has been replaced from the jeep with one that didn't have any codes so very doubtful a chaffed wire or connection problem given what has been checked so far. It has been a consistent issue not intermittent. The code has been there from day of purchase a year ago. It could be the pcm, just didn't want to put I another because this is the second one. Thanks for hanging in there Frank, I'll do some more checking, seems like it'll drive me crazy. Just hoping to solve the issue for his sake. Thanks again.

 

Wouldn't checking for continuity on the IAC to the PCM indicate a wire chafing or ground problem? I did check the pcm for ground and all seems fine. I'm beginning to think a new pcm might be in order. Any idea where to send it out to, other than dealer. They seem high in cost. Thanks again.

 

On the 16th you replied that the code was cleared for a few runs at least. For that reason i called it intermittent. When you check a wire for continuity, you only check if there is no wire breakage or bad connection somewhere, you will not see if the wire is shorted to ground for example. For that reason you should measure between each wire and a known good ground. You said that you changed the wire harness, but you also mentioned you found a wire problem and spliced a new wire in. Was this with the new harness?
While measuring for continuity or short, you will have to move the wires, to detect any internal wire breakage or intermittent short to ground.
You said that you tried an other PCM already and that the code was still the same, so it seems to be doubtfull that the PCM is the problem.
When you need it, you can contact these guys and ask for a quote for PCM repair or exchange: http://www.ecmtogo.com/

 

Again thanks for your patience Frank. Your right chk engine light went out for several days just prior to last inspection, which it passed then returned after and has been on since. I will check for ground problems later today and let you know how I make out. The pcm was replaced when the wiring was being done and all the codes thrown, then they had a lock out, I don't know why all I know is the pcm they said was bad and I had to get a new one, I sent out and got a new pcm for him which solved all code issues except the 505 code. Because of the labor I was hoping I could solve his issue here. Still hoping, he's using my truck and the car is here. The harness is a new one from my totaled GC that had no codes. Anyhow the saga continues. Thanks again.

 

You don´t have warranty on the PCM? So the wire repair you did was on the old wire harness and lateron you swapped the harness?

 

The old harness had the wire repair. This is a whole new harness. The computer was sent to Florida to have the key lock out removed, they called and said it was toast. They sent up another and I can't find the address or name of the outfit, I'm still looking. I think I found them on ebay. In any case no warranty mentioned that I can remember. Did check to see if any wires were grounded, none found. Checked to make sure all the grounds were good and they are. PCM to mounting bracket, mounting bracket to firewall, ground strap to mounting bracket.

 

There is no placard on the new PCM from that company you bought it from?

 

Just a short update, fuel gauge wire was corroded just outside just prior to going through rear floor, now working. All engine codes cleared with third cpu, no shorts were ever found. Runs fine and passed emissions test. It was on the back burner and finally finished it last weekend. Thanks for all the advice.

 

Thanks for the update. Good to know that you finally found it. Happy jeeping.:thumbsup:

 

I like the Jeep. V8 4 wheel drive but not taken care of by previous owner. I am not a good mechanic but I will drop off and have the wires traced like you stated and hope this will solve the problem.