Posted this question in my other post--When I ran a hot lead to a pin out in my ecm it touched the body of the ecm(metal case)and it sparked--Did I fry it?? Not sure if I did--Watcha think??

 

I only know for sure about Ford's ECMs, but I imagine that GM's ECMs are similar in that they sink current. That is, a solenoid under control of the ECM will be wired so that it is connected to +12V on one side and connected to the ECM on the other. To actuate the solenoid, the ECM grounds the side wired to it.

If you shorted one of those to the case of the ECM, no harm was done.

Only way to know for sure is to look at a wiring diagram and see what is connected to the pin you shorted to ground.

 

I'm sorry I wasn't exactly clear--what I did was I grounded a hot wire(sparked)to the body of the ecm, not any specific pinout.
Like when you have a static charge in your hand and you touch something--but I touched the body of the ecm w/a hot lead--didn't blow the fuse. Think I blew the ecm?

 

The metal case of the ECM is tied to ground, so if you touched a hot wire to it the ECM would most likely not have been harmed because the current would have gone straight to ground thru the metal case of the ECM without affecting the circuits inside.

 

Wow if that's the case I'm lucky!! Doesn't matter if the ecm was pulled down laying on the floor of the car? Sorry for the dumb question but the car still isn't running and I don't need another problem.
Thanks!

 

The ECM case is internally connected to ground, so even if it were lying on the floor of the car as long as it was attached to the harness it would be grounded.


Have you tried jumping the A and B terminals on the ALDL to see if you get a blinking "service engine soon" light? If you do then it's unlikely the ECM is fried.

Brian

 

I tried to do that before w/o any luck, that was part of the reason I was messing w/it.
Just in case I did change the check engine bulb, so it is a good bulb.
Any other ideas? Any direction would help me at this point.

 

Check that the bulb is getting 12V power when the key is in the ON position. The ECM grounds the other side of the bulb to turn it on, so if the bulb isn't getting power that could be why it's not coming on.

 

OK, I'll have to check which pin it is(behind the gauges)What if it isn't getting power? I don't think it is because the ecm isn't getting power either. Also the inj. weren't hot either--thus the hot wire to it.

 

If the bulb is not getting power check that the gages fuse is OK and getting power with the key in the ON position. If it's OK but not getting power the problem is somewhere between the battery and the fusebox.

Also check the ECM fuse..if it's OK but not getting power in the ON position, same thing.

Brian

 

Already checked the gage fuses under the dash and the fuse coming from the battery --all fuses were good, and the battery fuse was unbroken and getting power on both sides of the fuse. It's very frustrating!!
Any other ideas?

 

Only thing I can think of is that the harness to the ECM is bad. Try disconnecting it and grounding the pin for the SES light to see if it turns on. Also check for voltage on the power pin.

If the harness is good then the ECM may be bad..but shorting the wire against it probably isn't what killed it.


Brian

 

OK Brian I'll definitely check the ecm harness--what should I look for tho? I assume burns or breaks? I think that's the only thing I haven't checked yet.
What would be a good way of grounding out the ses light?
Thanks again for all your help!!