Pcm swap???

Kevin 007

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Whatever works for you. PCMS and IDMS are damn reliable on these trucks...they rarely fail unless someone is monkeying with them.

I'll give you the CPS failure...it has been a minor issue. I've replace one in each of my trucks....over the course of 466k miles combined. Some trucks eat them more than others...if so why not keep a spare and a 10mm wrench in the glove box if your paranoid over a sudden failure instead of replacing perfectly working components?

Paranoid? Nah...didn't say that. This is a forum, im adding my opinion just like you; for all of us to read, think about, share and learn from. Take from it what you will.

And I do carry a spare cps. And yes, the IDM's and PCM's have been reliable in these trucks along with many other electronic components, BUT; back to my original point, these trucks ARE aging if we like it or not. And more and more electronic failures are certain and the idms and pcms are starting to fail on occasion and undoubtedly they will do so more often in the future. I will keep running these trucks but sourcing QUALITY electronic parts in the future may become an issue; in fact its starting to already....which was another initial point I was trying to make.

Just food for thought....that's all.
 

90f250

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Well I'm beyond pissed at the moment... new good computer and even a fuse box and still...no wts, no fuel pump, no tach when cranking... what the hell am I missing?
 

Kevin 007

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Did you check the 30amp mini fuse in the in cab fuse box, not sure the number but it sends power to the ECM. Those symptoms present themselves when that circuit is dead. Its right at the bottom on one of the rows but check a diagram to be sure which one or just check all the fuses and make sure they are all good/or find a blown one which might be your problem

I make sure that I carry a few spare 30 amps in case. Its also a good fuse to pull if your gonna leave your truck unattended in some back alley and you want it to still be there when you get back....good/free anti theft measure
 

90f250

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Did you check the 30amp mini fuse in the in cab fuse box, not sure the number but it sends power to the ECM. Those symptoms present themselves when that circuit is dead. Its right at the bottom on one of the rows but check a diagram to be sure which one or just check all the fuses and make sure they are all good/or find a blown one which might be your problem

I make sure that I carry a few spare 30 amps in case. Its also a good fuse to pull if your gonna leave your truck unattended in some back alley and you want it to still be there when you get back....good/free anti theft measure


Yes all fuses, relays and wiring are all good so far. I have constant power on 1 wire to pcm, and key on power to the other 2 pcm power wires also. And I even checked that all 4 ground wires from pcm are good.
 

90f250

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This is what's odd. Pcm is getting power and ground both, yet it acts as if that pcm circuit is bad, the one that controls glow plugs and wts light, fuel pump, tach, and cig lighter
 

snicklas

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Yes all fuses, relays and wiring are all good so far. I have constant power on 1 wire to pcm, and key on power to the other 2 pcm power wires also. And I even checked that all 4 ground wires from pcm are good.

OK. Have you tested the power fuse, or have you replaced it?

If you haven't replaced it, please do. I know of someone that on a newer truck (6.0 Powered Truck) having a strange issue with the A/C and a couple other things. All the fused check out good, traced the wiring and there was voltage on a meter when tested. They finally cried "uncle" and took the truck to the dealer. The diagnostics, and the computer even told the dealer tech to replace the fuse. The dealer tech checked the fuse and there was voltage etc. He also agreed it had to be something else, not the fuse. Made a couple other checks, ran the diagnostics, and yet again, the computer said to replace that fuse. So finally, to prove the computer wrong, they pulled the "good" fuse and replaced it with a brand new one. Everything worked. The fuse had a crack in it that was almost invisible, that allowed voltage to be present when testing, but not deliver any current when the demand was made......
 

90f250

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OK. Have you tested the power fuse, or have you replaced it?

If you haven't replaced it, please do. I know of someone that on a newer truck (6.0 Powered Truck) having a strange issue with the A/C and a couple other things. All the fused check out good, traced the wiring and there was voltage on a meter when tested. They finally cried "uncle" and took the truck to the dealer. The diagnostics, and the computer even told the dealer tech to replace the fuse. The dealer tech checked the fuse and there was voltage etc. He also agreed it had to be something else, not the fuse. Made a couple other checks, ran the diagnostics, and yet again, the computer said to replace that fuse. So finally, to prove the computer wrong, they pulled the "good" fuse and replaced it with a brand new one. Everything worked. The fuse had a crack in it that was almost invisible, that allowed voltage to be present when testing, but not deliver any current when the demand was made......


The 20 amp maxi fuse? Changed to to be sure. Still nothing
 

snicklas

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Is that the only fuse that controls the PCM? I'm not familiar with the 7.3 in the OBS or SD's....
 

90f250

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Is that the only fuse that controls the PCM? I'm not familiar with the 7.3 in the OBS or SD's....


Yes, #19 is pcm and fuel pump fuse. That's the only one for pcm other than relay and a diode. All 3 check out working good and I've swapped them all too
 

90f250

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This may be a dumb question but with everything checking out good, is there a possibility that the CPS or the idm may be bad? I dont see how it would have happened since it ran fine before I swapped the gem and now nothing works, even old gem. New known good computer, new fuse box, all good relays and fuses, all wiring looks to be good and power to pcm and grounds as well.. I just dont see where anything else could have went bad. All the symptoms go to the pcm circuit but the circuit all tests good...this is extremely frustrating and I dont want to keep throwing time and money to it unless I absolutely have to
 

79jasper

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I'm not sure when Ford started using them, but do you have a chip key by chance?
What about the keyless entry pad?

Sent from my SM-N960U using Tapatalk
 

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