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Bad PCM?

12749 Views 5 Replies 5 Participants Last post by  DavidD
My 97 died the other night. No rpm's while cranking, no wait to start light. Check engine light on. Fuse 22 was NOT blown, nor were any others (except the trailer battery charge fuse #18, explained by a recent trailer wiring job) All the fuses have power to them and thru them and all were checked with a meter. I tested the 6 relays at the UH fuse location. I put in my spare CPS. The batteries are very old, but it cranks strongly and my smart charger indicates no problems with them. There were no intermittent problems leading up to this. After reading lots of threads, it seems the combination of no tach and no WTS light and no blown fuses point towards the PCM. I do not have a scan tool, but may have to buy one.
Have I missed anything? Are there any other relays I need to test? What does a PCM cost and who has the connection that can save me $$. Speaking of connections, are there any I need to check, other than at the PCM itself. Do PCM's just abrubptly fail like that or is it likely something shorted it out, even without blowing a fuse? I'll try anything you all can throw at me. Thank you!
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Depending on what happened (if anything) to the pCM, it may not communicate with a scan tool (and if you get one make sure it works on the Ford Diesels!). I had the PCM go bad on my 94 and the only thing it wouldn't do was power up the IPR (it would communicate with my scan tool, run KOEO tests, etc.). Do you have a chip installed? If so, remove it and see if that solves it. I don't have the PCM connector pinout handy, but if you can find it, you may want to check for power out to the PCM connector pins. Assuming your truck is not a California truck with splitshot injectors (PCMs are hard to get for these), you could try someplace like RockAuto for a PCM (I picked one up from them for $115 plus refundable core). Cheers!
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