That tan DLC wire splices into three other tan wires under a lot of tape in the wiring harness. My question is that if this connection went faulty, would that or could that cause fans to randomly come on and the pcm to reset randomly with the fuel priming and everything that normally happens on initial key on?

If so then I think I finally found my terrible wiring short. The tan wire was very stiff and I was wiggling it and there was lots of craziness going on. Then I straightened it out with my fingers and now it's not acting up. I'll have to cut out that section and patch it in the morning. I'm exhausted.

If that's not it, it's going to be a long week. I have no clue outside of that, but it just has to be. I don't know anything else that would cause the computer to reset and the fans to go crazy like that all in one bad wire.

 

If it was touching ground it would cause a problem. It could have pulled the 5 volt reference down in the PCM accounting for the appearance of resetting. Sounds like someone was doing some wiring before. You may want to check the other splice about a foot further back on the black/white wire to see if that had been messed with also.

Hope it fixes your problem.

 

It was all still in the factory wrap. It was just a factory joint of four tan wires. One of the wires seems very stiff like it's been having a bad connection and building up resistance. What if it was just losing and getting power to the wire that goes to the pcm in just the tan wire by itself. Like the connection was intermittent so the key is on and power cuts to teh tan wire for a second beacuse of the bad connection on the tan wire, then goes back on then off on..etc. Would that reset the pcm in itself? Seems like if the power stopped coming through the tan wire to the pcm that it would be almost like turning the key on and off. Which is what the problem acts like.. only with the additional fans flickering on and off. Like say the voltage drop is all in the connection and so sometimes it drops to nothing and others to 5v and others to 2 or 4.

Which direction is the other one that you say is a foot further back? Towards the pcm or towards the fuse box? The tan wire was in the direction of the pcm coming from the dlc connector location.

I pray that none of you ever experience a wiring short... man this has been the hardest to find. It really has to be this wire.. I just can't imagine what else. I checked all the computer wires relating to power the pcm in the fuse box and wiggled the crap out of those wires and got nothing.

 

The tan wire is not a power wire. It is the serial data wire for computer access (PCM, EBCM, SIR). Still, if it were getting grounded out, it might cause some problems. If it were merely open, it should not cause a problem.

 

Well, what else does it connect to? One splits off to the computer, one goes to the dlc and another off into the wiring somewheres.

How does a signal data wire send a signal? Wouldn't it have to have power going through it?

Does the tan wire carry a signal to start all the initial functions when the car is first powered on? If so then if there's a variable resistance across it from a bad connection wouldn't it mess up the signal and get corrupted and misinterpreeted by the computer?

I'm just trying to figure out what's going on here... it's not exactly clear to me how the computer knows to start the fuel pump for a few seconds and cycle the fans when you first turn the key. It seems like this is the problem in one wire that controls that. The only wire I know of that has that kind of effect is in that DLC. But any ideas on this are welcome. I just don't see anything it could be grounding on. What about if the black wire doesn't ground out when it should due to resistance somewhere or a bad connection?

 

I listed what it connects to: PCM, EBCM, SIR and then the DLC. It's the data line that connects these modules. It will have a modulating signal on it, but it doesn't not go back to a fuse. The wire at the DLC is just for scanner access.
The computer does those other things by virtue of it's programming.

 

Yeah, i follow but what wire sends the signal or power to the computer to start executing the program.

In any event.. last night it was really late and when i messed with that wire it acted up real badly.. I straightened the wire out with my fingers and kind of squeezed the connection to make sure all the wires were straight and now the car runs fine. Now that it's not 2am and I could get back out to the garage I tested that tan wire. It carries 5v or about 4.5 at the moment. To me it seems like if that voltage could not get from wherever it's coming from to the pcm that the PCM would not start sequence.. or if there were extra resistance on the wire from a bad connection the computer would reset itself as it got too far from 5v. In any case I hope that's all it was. I'm going to cut the wire and put it together and take it apart while the key is on to see if that duplicates the problem if so I'm sure that's all it was.

Thanks for hanging in and troubleshooting with me.

 

Just like your PC, power is supplied to the main board of the computer and the computer does it's thing according to the programming it has stored. There are a couple of PCM ignition feeds (hot with the key ON) and one power feed that stays hot all the time (that is the one that you have to kill the power on to reset the computer).

 

Ok.. did some more testing. Guess it wasn't that tan wire. That just keeps a constant 4.6~5v.

Anyway, after testing some connections to the pcm at those three connectors I found a pink wire that causes the pcm to reset. So I went back to the fuse box where there's a pink power wire and it's at the PCM ign fuse. When I pull the PCM ign fuse in and out like a loose connection it duplicates my exact problem... sooooooo it would seem that i finally figured out what circuit the problem is on. Unfortunately at the moment it's not acting up so I'm having a hard time diagnosing which wires from that circuit it is. There's a pink power that I think comes off the ignition switch to some other wires and through that box i was trying to show earlier in the other thread.. and then into the fuse box. There's the thin pink wire that i guess goes to the pcm. Beyond that I don't know.

Does anyone know if that circuit has a shared ground or an isolated ground? If it's shared then I'd have to figure the problem is in the power wires because nothing else is acting up.

What's the best way to test? Maybe pull the ignition connector, and check resistance between the pink ignition wire and the big box that everything runs into.. and then from that wire to the fuse box? What would be an abnormal reading? 20+ohms or what?

It seems to make sense that this is the problem. The previous owner had a remote start or something with a lot of quick splices on the ignition wires and I bet the poor connectors caused an increased resistance which ruined the wire.