Cliff notes - While wiring electric water pump, I think I tripped/fried the theft deterrant module on my car... that i didnt even know it had until now. Or possibly fried the PCM.


going to keep this short as i possibly can: Tonight I was over my buddies wiring the relay harness for my electric water pump. I couldnt really find any "popular" choice for a 12v signal for the ewp relay on this board, so I thought I would be creative and use the same signal as the fuel pump, since that has a nice automatic function to it. (shuts off when engine doesnt start).

I looked up the wire in a haynes manual, A25, and spliced it in. *THIS ISNT CORRECT* (also can be found here: http://shbox.com/1/1995_pcm4.jpg). I turned the ignition a couple times and it sounded like everything was working as it should be! So i cranked it over and it fired up... but it immediately died. This didnt alarm me since I just did a cam swap and the tune isnt right. Fired it again and exact same thing. but this time all the lights went out and the car went COMPLETELY dead as if there were no battery even connected.

So, fast forward a little and this is about when I double checked the schematic and noticed where that signal wire was going ... the theft deterrant module, instead of the fuel pump. Yea, brilliant of me.

In the time I had, I managed to track down the relay for this module and test that it is functioning correctly. I was hoping I just fried that relay but no dice. the PCM also SEEMS to be OK considering everything comes back when the battery disconnected/reconnected, but it goes out the instant ignition is turned.

Can anyone here either tell me what I did, or if not tell me where the theft module is? Or any other ideas? I want to get the car out of my friends garage. I have already removed the splice, if that wasnt obvious.

 

appears as though this guy wired it the same way, so maybe i didnt wire it wrong??

https://www.camaroz28.com/forums/sho...d.php?t=445168

 

You don't want to use A25. That is the signal from the VATS to the PCM (to enable (allow) fuel delivery). It is a modulated ground, not a true ground.

It's entirely possible (not saying probable) you could have damaged the PCM by whatever current you ran to that wire. If you have VATS programmed out, that might (guessing) restore function if you caused a problem.

 

I took the PCM apart and inspected it (i ocasionally repair circuit boards at work), and it looked fine, although that doesnt mean anything with sensitive chips.

Honestly I would almost prefer I cooked my PCM at this point than to have to deal with bypassing VATS.

I definitely read your schematic the opposite of what you just said as far as the direction of the signal.

 

OK ive been reading here that the VATS system should be throwing a security light on my dashboard. My car does NOTHING... leads me to believe the PCM is toast. I really dont understand how I fried this thing, the wire from my relay shouldnt have had any current coming from it. I could see the added resistance messing with the original signal at most, but not frying. Guess im not an electrical genious.

 

Just throwing this out there since it wasn't in your previous posts, but did you check your fuses? Try checking the whole length of the wire you spliced into as well, preferably with a multimeter. You could have fried part of it. I would check those first before you go assuming the PCM is toast.

 

The thing is the car will have all power or none at all. i did check 85% of the fuses though (whatever ones came out with my fingers). It doesnt seem to be a fuse issue. There isnt much room to "check the whole length of the wire."

When i reconnect the battery the car has also lost power all by itself...without me even turning the ignition. Just randomly goes out.

I also noticed that when reconnecting the battery, i dont get any sparks on the battery terminals. The draw is extremely weak.

 

Man I hate wires, just for this reason. I am tagging along for the ride since I have a EWP to wire later on.

Good luck.

 

I picked up a new PCM today out of an old Caddy fleetwood so I am gonna try that first thing after work.

Someone on LS1tech posted that i *should* have spliced pin A7 instead. Right now its just looking like I grounded the thing out some freak way.

 

A7 is the fuel pump relay control...

 

you can call me an idiot, I can handle it!

 

No need to do that. It's all a learning process.

 

Well, I found a loose connection at the power hub (that we never touched). I plugged the new PCM in and it fired right up. Sure enough the original PCM is working now too.

Oh well, i have a spare PCM now - probably a matter of time before I smoke one anyway