EFIDynoTuning Forum

So my PCM has been reporting Vref errors on forscan for a hot minute, like 1.5 years now.


Previously it would report voltage, not the right voltage, but it would report voltage.


No symptoms previously, other than the reported inferred vacuum reading was oscillating wildly. No biggie, PCM baro is locked at 1 atmosphere in tune right?


Well, I accidently flipped polarity on 2 alternators after installing a new engine, it hasnt wanted to run for ish since And Forscan is just erroring out on the reported VREF now.


I have checked the sensors being fed a 5v and the only one that is off is the IAT plug by .5v, the rest report 4.97v



Symptoms include running like trash with the MAF and TPS plugged in, Rolling misses, backfires after unsuccessful start attempts and backfires at key off idling.



Ive got an alternator on it with known good diodes now, and all of my sensors are testing out fine.



Just looking for some way to confirm the PCM is dead besides setting more money on fire.

sounds like it

you can usually snatch an ecu at your local u pull it for $30 or so

yeah the ml2872 hardware code that matches your tunes for this is actually rare.


talking cheapest I can find used is $200 and the cheapest reman is $400+

If I could find the pinout differences between ml2871 and ml2872 to figure out if the ml2871 hardware coded PCM's are useable that would be awesome.
'

the ml2871's PCM's are cheap and plentiful.

all 98s are interchangeable even the crown vics if u needed to

When you say interchangeable do you mean 0 repinning required?


Because that would be freaking awesome.

Yup 98 vic at the local upullit yard $50 after tax.


If i could just slap the quarterhorse in the back of it and go that would be amazing.

yep no prob

What about a 98 f150 pcm?


The vic ones already gone lol

Guessing thats a negative?

cant vouch for that

if your going to get a new ecu why not just upgrade to the best ?

03/04 luxury sedan

youll have to move the fan pins and your tach may not work unless you swap to a 99-04 cluster but otherwise plug and play