Knowing a vehicle's past owners really helps when diagnosing a vehicle problem... 1989 Ford Club Wagon XLT 351w, c6

I bought a code reader for the OBD1 system and pulled the codes from my van, which are:

122 - Throttle Position Sensor below minimum voltage
621 - Shift Solenoid #1 Circuit Fault
622 - Shift Solenoid #2 Circuit Fault
624 - Electronic Pressure Control Solenoid Circuit Fault
626 - Coast Clutch Solenoid Circuit Fault
629 - Converter Clutch Solenoid Circuit Fault or Lock Up Solenoid Circuit Fault
637 - Transmission Oil Temperature Circuit Above Maximum Voltage
654 - Not in Park During KOEO Test

I was originally trying to count light flashes, but as you can see, there are a TON of codes.

Now I know of it's past 4 owners, 3 of them are Facebook friends. I recently posted the codes to a Facebook page and encountered the realization that my vehicle is equipped with a c6 transmission and should not be throwing any transmission codes. After an hour or two, a past owner commented on the post and told me that he had replaced the ECU in my van with one from a 351w with an automatic transmission WITH overdrive. The codes are starting to make sense.

My question is, how universal are ECUs? Would this alternate ECU be optimized for my engine? I haven't been able to achieve even decent MPG, even with a Gear Vendors Overdrive and I know next to nothing about ECUs.

Thanks!

 

ECU's are specific to the vehicle installed in. Just cant take one from one and put into another. When I changed the one in my 89 F250, had to give them the number on the device plus vin number all that stuff. So I would suspect you need to see if you can get a direct replacement not something from a junk yard for your specific vehicle.

 

ECUs are not specific to the vehicle installed in. While the VIN can be programmed into it, it doesn't have to be. You can just take one and put it in another. As long as the hardware in the truck matches what the ECU expects it's going to work. In the case here, the engines are the same, but the transmissions are different, hence all of the transmission codes. If you don't mind the transmission codes this ECU (Ford actually calls it a PCM - Powertrain Control Module) will work just fine.

 

PCMs are universal as long as they match the basic powertrain combo.. same engine and trans. In this case I think the number of codes being generated is affecting overall engine performance because the programming is designed to do things to protect what it sees as a crippled transmission. I think you would get better results with PCM designed for the 5.8/C6 combo you have.

 

After posting this, I contacted a Ford Guru from my local Volkswagen club, he's got an 89 e350 cutaway with a c6. He came to the same conclusion that Conanski came to, he told me that I would need a PCM with the beginning 4 digits of E8TF. He said something along the lines of, since the PCM only outputs in fuel sprays, and isn't adaptive, there's a chance that it's running extremely rich and it has the inability to re-learn. This is my first time dealing with PCMs.

Here's also a link he sent me for a used unit on eBay, in the lower portion of the listing it shows a compatibility table for me to reference at the junkyard this weekend.




https://www.ebay.com/itm/123716311217?ul_noapp=true

 

After a fair amount of research and talking with quite a few individuals, I just ordered a PCM from eBay that once controlled a 1989 Ford F250 with a manual transmission. My transmission being a c6, it should work, and it was pretty cheap. I offered $40 and managed to get it.

 

I hope yours works out.

I got one from Oriellys, it was a Cardone brand, supposedly preflashed and it made my van run like crap. I matched up all the numbers on mine to the reconditioned one and Oreillys confirmed it was the correct one.
It made my van run wild. I gave it some time to see if it needed to adjust but it never did.
I reinstalled my old one.

Good luck

 

Thanks! Yeah I'll definitely be keeping the other one for a bit until I see that it's sorted itself out and functions like it should. Might even just keep it for an overall spare.

 

An FYI for anybody that may read this thread, any place that claims one of these PCMs was reflashed should set a red flag, these PCMs cannot be reflashed because they do not contain any flash memory. Now there is a memory device inside but it's the old school ROM style which can be eased and reprogrammed but it takes a totally different procedure and I'm not sure it can be done with the chip in the PCM... it likely has to be removed first.