Dead PCM?
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From: Michigan
If there actually was a true short on that wire, then the pump would run even if the PCM was unplugged. The short would provide the ground path for the relay control circuit. I am real curious why you are seeing that reading though.... Somethin' ain't quite right.......
The 96 PCM should work.
The 96 PCM should work.
ive read that a short in a plug wire can fry a pcm and I tested the burned up one I pulled for resistance and it jumps all over the place when I wiggle it whereas the new ones I bought don’t. So if a plug wire CAN fry a pcm I suppose that would explain it.
Last edited by Packwood Digital; Aug 24, 2020 at 12:23 PM.
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From: Clayton MI
Plug wire won't fry a pcm, unless the spark arcs TO the pcm...... and it would have to be REAL lucky to hit it someplace that it really matters.
When testing resistance like that, I don't think the scale you use is really all that critical. Most meters are 'auto-ranging' to an extent anyway...... Changing the scale it is using just moves the decimal point around anyway.
When testing resistance like that, I don't think the scale you use is really all that critical. Most meters are 'auto-ranging' to an extent anyway...... Changing the scale it is using just moves the decimal point around anyway.
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Plug wire won't fry a pcm, unless the spark arcs TO the pcm...... and it would have to be REAL lucky to hit it someplace that it really matters.
When testing resistance like that, I don't think the scale you use is really all that critical. Most meters are 'auto-ranging' to an extent anyway...... Changing the scale it is using just moves the decimal point around anyway.
When testing resistance like that, I don't think the scale you use is really all that critical. Most meters are 'auto-ranging' to an extent anyway...... Changing the scale it is using just moves the decimal point around anyway.
used pcm s on eBay are like $50-60 bucks so it’s not the HUGEST deal if I do fry the next one but it will lead me back to square 1. But then again I will know for sure it’s “something else” causing it to fry.
is there any connector or switch or sensor that if it shorts it could fry the pcm?
I just had this weird feeling to check my o2 sensors just now because I put a new catalytic converter on the morning before I changed my plugs and when I looked at the pins on the truck side one of them was bent and literally touching another pin.
is it possible that two of the o2 sensor pins touching could create a short and fry it?
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From: Clayton MI
Shorted pins on a sensor could cause some issues, but, still, shouldn't fry the PCM. (the manufacturers have to realize that things like that WILL happen, even a sensor failure can cause shorts from one circuit to another.)
Blew the 30 amp fuse? What all is powered off of that?
Blew the 30 amp fuse? What all is powered off of that?
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Shorted pins on a sensor could cause some issues, but, still, shouldn't fry the PCM. (the manufacturers have to realize that things like that WILL happen, even a sensor failure can cause shorts from one circuit to another.)
Blew the 30 amp fuse? What all is powered off of that?
Blew the 30 amp fuse? What all is powered off of that?
the second time I tried to start it the check engine light didn’t come on anymore (even with key on)
Then I noticed the 30A engine fuse was blown (don’t know if it blew after the first try or second try to start)
i replaced it but it didn’t fix anything tried starting it several times after that but the fuse never blew again and is still good
im not 100% sure what it controls, I thought someone said it controls the ASD but I can’t find the quote now.
Last edited by Packwood Digital; Aug 24, 2020 at 01:46 PM.
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found it. In post #8 @DerTruck said the following:
:
Sure voltmeter works too. Fuse 6 in the PDC is the one labeled "engine cont" and is the one providing power to the ASD relay and from there to the injectors and coil.
My reasoning is: You had issues with the coil before, you worked in the vicinity of it and the fuse that blew provides power to the coil. So that's where I would start before swapping PCMs.
My reasoning is: You had issues with the coil before, you worked in the vicinity of it and the fuse that blew provides power to the coil. So that's where I would start before swapping PCMs.
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Ok, I got fuse 6 as a 40 amp, for the headlights/foglights. Fuse 4, the one circled, goes to the ASD relay. (I believe that's a 30 amp.)
ASD powers coil, and injectors, and has a feed back to the PCM to let it know that it is indeed on.
So, my question becomes....... what blew the fuse? I don't think a plug wire arcing to anything hitting that circuit would actually blow the fuse..... The voltage surge *might* fry the PCM...... but, the odds on that are WAY out there...... I wonder if the PCM didn't fry, and the PCM going out (and drawing too much current on that circuit) blew the fuse....... But, I would almost expect that if that were the case, it would suck the fuse each and every time the PCM triggered the ASD relay... but it's apparently not doing that.
Are you still getting the code for No ASD output?? If you are, that whole circuit in the PCM may have toasted, so, there is no ground path there any more......
Congrats,
You came up with truly odd one.
ASD powers coil, and injectors, and has a feed back to the PCM to let it know that it is indeed on.
So, my question becomes....... what blew the fuse? I don't think a plug wire arcing to anything hitting that circuit would actually blow the fuse..... The voltage surge *might* fry the PCM...... but, the odds on that are WAY out there...... I wonder if the PCM didn't fry, and the PCM going out (and drawing too much current on that circuit) blew the fuse....... But, I would almost expect that if that were the case, it would suck the fuse each and every time the PCM triggered the ASD relay... but it's apparently not doing that.
Are you still getting the code for No ASD output?? If you are, that whole circuit in the PCM may have toasted, so, there is no ground path there any more......
Congrats,
You came up with truly odd one.
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Ok, I got fuse 6 as a 40 amp, for the headlights/foglights. Fuse 4, the one circled, goes to the ASD relay. (I believe that's a 30 amp.)
ASD powers coil, and injectors, and has a feed back to the PCM to let it know that it is indeed on.
So, my question becomes....... what blew the fuse? I don't think a plug wire arcing to anything hitting that circuit would actually blow the fuse..... The voltage surge *might* fry the PCM...... but, the odds on that are WAY out there...... I wonder if the PCM didn't fry, and the PCM going out (and drawing too much current on that circuit) blew the fuse....... But, I would almost expect that if that were the case, it would suck the fuse each and every time the PCM triggered the ASD relay... but it's apparently not doing that.
Are you still getting the code for No ASD output?? If you are, that whole circuit in the PCM may have toasted, so, there is no ground path there any more......
Congrats, You came up with truly odd one.
ASD powers coil, and injectors, and has a feed back to the PCM to let it know that it is indeed on.
So, my question becomes....... what blew the fuse? I don't think a plug wire arcing to anything hitting that circuit would actually blow the fuse..... The voltage surge *might* fry the PCM...... but, the odds on that are WAY out there...... I wonder if the PCM didn't fry, and the PCM going out (and drawing too much current on that circuit) blew the fuse....... But, I would almost expect that if that were the case, it would suck the fuse each and every time the PCM triggered the ASD relay... but it's apparently not doing that.
Are you still getting the code for No ASD output?? If you are, that whole circuit in the PCM may have toasted, so, there is no ground path there any more......
Congrats,
You came up with truly odd one. my thinking is that the pcm fried and took the fuse with it on the first no start (it started for literally half a second then died and displayed the ASD code) but after that the pcm was too dead to do any more damage or even illuminate the CeL anymore and now just acts “weird” with whatever juice it has left (I.e. making the pump run non stop)
Yea, thanks. Do I get an award? LOLOLOLOLOL.
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From: Clayton MI
The CEL no longer comes on at all even with key on. When I connect a scanner it fails and won’t see the computer.
my thinking is that the pcm fried and took the fuse with it on the first no start (it started for literally half a second then died and displayed the ASD code) but after that the pcm was too dead to do any more damage or even illuminate the CeL anymore and now just acts “weird” with whatever juice it has left (I.e. making the pump run non stop)
Yea, thanks. Do I get an award? LOLOLOLOLOL.
my thinking is that the pcm fried and took the fuse with it on the first no start (it started for literally half a second then died and displayed the ASD code) but after that the pcm was too dead to do any more damage or even illuminate the CeL anymore and now just acts “weird” with whatever juice it has left (I.e. making the pump run non stop)
Yea, thanks. Do I get an award? LOLOLOLOLOL.
An award? Probably, I will have to dig back into the archives, and see if I can find one.
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Ok, I got fuse 6 as a 40 amp, for the headlights/foglights. Fuse 4, the one circled, goes to the ASD relay. (I believe that's a 30 amp.)
ASD powers coil, and injectors, and has a feed back to the PCM to let it know that it is indeed on.
So, my question becomes....... what blew the fuse? I don't think a plug wire arcing to anything hitting that circuit would actually blow the fuse..... The voltage surge *might* fry the PCM...... but, the odds on that are WAY out there...... I wonder if the PCM didn't fry, and the PCM going out (and drawing too much current on that circuit) blew the fuse....... But, I would almost expect that if that were the case, it would suck the fuse each and every time the PCM triggered the ASD relay... but it's apparently not doing that.
Are you still getting the code for No ASD output?? If you are, that whole circuit in the PCM may have toasted, so, there is no ground path there any more......
Congrats, You came up with truly odd one.
ASD powers coil, and injectors, and has a feed back to the PCM to let it know that it is indeed on.
So, my question becomes....... what blew the fuse? I don't think a plug wire arcing to anything hitting that circuit would actually blow the fuse..... The voltage surge *might* fry the PCM...... but, the odds on that are WAY out there...... I wonder if the PCM didn't fry, and the PCM going out (and drawing too much current on that circuit) blew the fuse....... But, I would almost expect that if that were the case, it would suck the fuse each and every time the PCM triggered the ASD relay... but it's apparently not doing that.
Are you still getting the code for No ASD output?? If you are, that whole circuit in the PCM may have toasted, so, there is no ground path there any more......
Congrats,
You came up with truly odd one. In any case I'm worried that replacing the PCM either doesn't fix it or it gets fried again as we still don't know what really happened. I'm a little wary of the aftermarket coil. If the high voltage side for some reason arcs over to the control side I can see the PCM getting damaged. There isn't any benefit to running the MSD coil as the truck does not have a high performance/high compression engine.
One idea I had was to remove the 30A fuse and the fuel pump and ASD relays. Make sure the ground at the front of the engine is good. Connect battery, turn on ignition and see if the OBD2 scanner can talk to the PCM again.