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Powertrain Control Module -- Part II


rumblecloud

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What's the worst that could happen?
This is the thing that makes it all go.
I recently had a bunch of different issues with rough and varying rpm/idle. Truck would lose all power and stall if I pressed too hard on the accelerator as in trying to hit passing gear. I did all the usual things like checking for vacuum leaks, checking the IAC, the thermostat and temperature sensor, throttle position, etc.

Finally pulled the PCM to check the capacitors as has been mentioned as a problem area that can cause all kinds of havoc. When I pulled it, I found that the capacitors were in pretty good condition -- really good considering they're over 25 years old. I did not replace them but I know I may have to at some point in the future per recommendations by RonD and others..

What I did do was clean the crap out of the ground wires from the PCM to the fender wall. The connection was in pretty bad shape -- green and crustry.

Turns out that that simple ten minute job appears to have solved the problems I was having. The ground connection sits right below the cruise control servo (if you have cruise), just above and forward of where the PCM sticks out of the firewall.

20221009_165145.jpg

Lesson ;earned and am posting here to remind y'all. Thanks to RonD fro all the help with my troubles.

r
 


RobbieD

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Toonces drives a Ranger . . . . just not very well.
Bad grounds can create the weirdest problems, and they can be tough to find. You did real good in getting your truck sorted out, and thanks for posting what finally fixed it.
 

19Walt93

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If you don't have time to do it right will you have time to do it over?
Good job but that part wasn't a PCM, it was called a processor and all it controlled was the engine- and torque convertor lock up if you had an automatic.
We sold a new Explorer to a long time, loyal customer in the early 2000's. It was towed back in with a no start within the first week or so and testing found no dtcs, it just wouldn't start. The tech who fixed was about the best I ever had, he found that the ground for the PCM had .7 ohms of resistance. The spec is .2ohms or less. He removed the ground screw, scraped a little paint off the core support, and reattached the ground. We returned it to the customer after a road test and he drove it for years, he's since died and his wife still drives it.
Not everything is simple or easy to find but it's always a good idea to check all the grounds before doing anything major or expensive. Check means remove and inspect, not just eyeball them.
 

rumblecloud

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Ranger Splash
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4.0 V6
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Automatic
2WD / 4WD
4WD
Total Lift
1-1/2 inch front leveling
Total Drop
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31/10.50/15
My credo
What's the worst that could happen?
Good job but that part wasn't a PCM, it was called a processor and all it controlled was the engine- and torque convertor lock up if you had an automatic.
Is this a terminology thing? Just curious.
Is there a PCM (Powertrain Control Module)? And if there is, where is it? The EVTM calls something a Powertrain Control Module. I thought that that something was what I pulled to check the capacitors.

Again, just curious. I don't want to go leading someone astray and be stupid while I'm doing it.

Thanks.
r
 

19Walt93

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Ford Ranger
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Engine Size
351
Transmission
Automatic
2WD / 4WD
2WD
Total Drop
3"
Tire Size
235/55R16
My credo
If you don't have time to do it right will you have time to do it over?
PCM appeared with OBD II when common (mostly GM) terminology was mandated. Ford called it a processor for EEC I through IV when GM was calling theirs an ECM. Once the processor started controlling convertor lock up I suppose it actually was a PCM in function. Part names are kind of a pet peeve with me, for example: no Ford ever had a Posi, that was Chevy's name for their weak kneed limited slip. A Posi is the rear end the high performance Chevy guys replaced with a Ford 9 inch because they got sick of it breaking. A Ford pickup with space behind the seat is a Supercab, not an extra cab or extended cab. The steel or aluminum part the tires are mounted on is a wheel, a rim is only part of a wheel.
 

rumblecloud

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Vehicle Year
1994
Make / Model
Ranger Splash
Engine Type
4.0 V6
Transmission
Automatic
2WD / 4WD
4WD
Total Lift
1-1/2 inch front leveling
Total Drop
Stock
Tire Size
31/10.50/15
My credo
What's the worst that could happen?
I wrote Ford sales brochures from 1980 thru about 1995 or 6. So I am familiar with the SuperCab, Crew Cab terminology and the EECIV stuff.
All the Ranger sales brochures (and Mustangs) thru that period are mine.

Anyway, thanks for the response.
 

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