97 PCM Acting Up?

[AlaskanEngineer]

I have a friend who used to live up here calling for some advice, and I am coming up empty right now and was hoping someone else out there could chime in.

He has a 97 7.3 with Manual Tranny, that recently developed a no-start condition. It was towed to a local dealer and they eventually arrived at a PCM problem due to evidence of corrosion. They say that if they gently tap the PCM with a hammer, it will consistently allow the truck to crank. My friend has since ordered a PCM from an auto parts warehouse, had it installed and NOTHING, and based on the Ford dealership saying it must be defective, he sent it back to get a replacement from the same company, which just arrived and is also doing nothing, while the original will still allow the truck to start if you give it a sharp rap with a hammer.

I am going to try to set my friend up with an account here at the org so he can respond to this thread and eliminate the middle man as soon as possible, however wanted to get people's mental gears turning as soon as possible. I/He will post the PCM calibration codes as soon as we can find them. Apparently no fuses have been blown so far, at least none on the truck anyhow The dealership also says they have determined the PCM is getting power...

Ideas?

[Patrick Feeley]

How does the wiring and pins on the PCM connector look? I think I'd be looking there too. Is the wait-to-start light coming on? Is the CEL illuminated? Cheers!

[madpogue]

Originally Posted by AlaskanEngineer

They say that if they gently tap the PCM with a hammer, it will consistently allow the truck to crank.

Maybe you mean it allows it to _start_. It should crank even with NO PCM installed.

My friend has since ordered a PCM from an auto parts warehouse, had it installed and NOTHING, and based on the Ford dealership saying it must be defective, he sent it back to get a replacement from the same company, which just arrived and is also doing nothing, while the original will still allow the truck to start if you give it a sharp rap with a hammer.

With the aftermarket PCM, does the WTS light come on? Does the Check Engine light blink super-quick (like, 1/10 second) when you turn the key to RUN? Does the tach respond when you turn the key to START? Any white smoke?

And just to be sure, is it def. the PCM the dealer is talking about, and not the IDM? The IDMs are known to flake out when they get water in them.

[gaspipe]

I'd also look at the relays by the airbox. They can create similar symptoms when they are approaching death. IIRC, #1 and/or #2 are the ones.

[BigFuel]

Is the dealership tapping inside the fender or behind the parking brake?

[AlaskanEngineer]

Well, I spoke with my Friend on Friday night, he should be able to start posting as soon as he gets back to a computer Monday-ish. In the meantime I am going to relay his message to me here for everyone (at bottom)

The above questions are very much appreciated (WTS light, CEL light, and Relays) - Also will try to find out the answers to the questions about condition of the pcm plug, and the physical location of the tapping with the hammer - should find something out tomorrow (Monday) along with the answer from Cardone (see below)

Originally Posted by madpogue
Maybe you mean it allows it to _start_. It should crank even with NO PCM installed.

- Yes you are correct: meant allows it to start.

His message below:
"I appreciate the help on troubleshooting the PCM. I called Cardone to see if I was getting the correct PCM and they said they would cross reference it with the Ford OEM part number. Ford part number is F7TZ-12A650-SB. Autopartswarehouse has sent me 2 PCM's. They sent me Cardone Part number: 78-7066. The Ford diesel mechanic says these two PCM's may be the wrong part since I did not give my VIN and mileage to the autowarehouseparts representative when I ordered the PCM.

I am attempting to cross-reference the Cardone part number with the Ford part number. Cardone is closed on the weekend, so I will have to wait until Monday unless someone else has an idea? "