pcm fuse keeps blowing

[cjs04eddie]

i have a 2004 ford explorer with the 4.6l v8 was driving it a couple days ago and all of my gauges started to turn on and off and my windows and lock button etc stopped working right before i pulled in it started to misfire really bad all while reading over 18v on my after market voltage meter figured the regulator in the altenator died turned it off and back on again to look into it more and the vehicle completely shut off later realized that the pcm fuse blows every time i turn the key anybody know what’s wrong with it ?

 

[Fix4Dirt]

i have a 2004 ford explorer with the 4.6l v8 was driving it a couple days ago and all of my gauges started to turn on and off and my windows and lock button etc stopped working right before i pulled in it started to misfire really bad all while reading over 18v on my after market voltage meter figured the regulator in the altenator died turned it off and back on again to look into it more and the vehicle completely shut off later realized that the pcm fuse blows every time i turn the key anybody know what’s wrong with it ?

not sure about the 18v, but ive heard stuff like wiring short out to exhaust or injector wiring to intake cause it to pop fuses. @Lee's Automotive having similiar issue.

 

[Lee's Automotive]

not sure about the 18v, but ive heard stuff like wiring short out to exhaust or injector wiring to intake cause it to pop fuses. @Lee's Automotive having similiar issue.

Pcm fuse is good still can't find anything blown

 

[Fix4Dirt]

Pcm fuse is good still can't find anything blown

didnt it pop once?

 

[Lee's Automotive]

didnt it pop once?

Yep i believe it was the knock sensor that grounded that caused that though

 

[Fix4Dirt]

Yep i believe it was the knock sensor that grounded that caused that though

oh ok nvm then sorry still 8 my brain isnt supporting peak capacity yet

 

[Lee's Automotive]

oh ok nvm then sorry still 8 my brain isnt supporting peak capacity yet

My brain is still running away from me I'm trying to find it now

 

[Fix4Dirt]

My brain is still running away from me I'm trying to find it now

same man cant seem to find it! now where did i leave that socket...

 

[Lee's Automotive]

same man cant seem to find it! now where did i leave that socket...

Or better question where did i leave the tool bag?

 

[Fix4Dirt]

Or better question where did i leave the tool bag?

"what timezone am i in? what country am i in? doesnt matter its always 5 oclock"

 

[J_C]

I would guess that your assessment is correct, that the voltage regulator in the alternator failed, put 18V through the system, which caused the voltage regulator in the PCM to fail from overheating... is probably a linear regulator so all excess voltage is converted to heat.

I could be wrong, especially newer like a 2004, would crack the PCM open and do some circuit tracing and measurement with a multimeter if you have the potential to desolder and solder in PCB components... or just as an autopsy to be certain the PCM itself is damaged before replacing it, and of course I'd measure resistance between the PCM power circuit the fuse is on, and chassis ground both with and without the PCM plugged in, just in case with it unplugged, it was a wiring short but that wouldn't cause 18V...

 

[cjs04eddie]

I would guess that your assessment is correct, that the voltage regulator in the alternator failed, put 18V through the system, which caused the voltage regulator in the PCM to fail from overheating... is probably a linear regulator so all excess voltage is converted to heat.

I could be wrong, especially newer like a 2004, would crack the PCM open and do some circuit tracing and measurement with a multimeter if you have the potential to desolder and solder in PCB components... or just as an autopsy to be certain the PCM itself is damaged before replacing it, and of course I'd measure resistance between the PCM power circuit the fuse is on, and chassis ground both with and without the PCM plugged in, just in case with it unplugged, it was a wiring short but that wouldn't cause 18V...

if it comes down to being the pcm i would rather just get another one then spending time trying to fix this one they really aren’t all that expensive anyway

 

[J_C]

^ Sure, but remember you need to program the keys in.