Ford Aerostar :: 1990 - Intermittent CEL On - ECU Dead?
May 7, 2012
I have had an intermittent Check Engine Light for a couple of days --- the van started and ran fine, but the CEL would come on after about 15 minutes of driving. It would sometimes go off before I reached my destination, but it was always off the next time I started the van. No sweat.
I went to read the codes this afternoon and now have a problem. I put one end of a jumper wire into the Self Test Input (STI) and then accidentally let the other end of the wire touch the 12V connector of the starter relay (why is that thing unprotected anyway?). I saw a little arc so I know there was some current flowing.
After this, I connected the STI to SIG RTN for reading the Key On Engine Off codes and got no pulses at all. I rechecked the jumper wire but got the same result. I then removed the jumper and started the van --- it ran quite rough and would only stay running by giving it plenty of gas. The CEL was on the whole time. I did this a couple of times just to be sure.
I guess there's nothing more annoying than turning a little problem into a big one... crap.
I couldn't find an electrical circuit diagram showing the STI in my Haynes manual, so I'm not sure what is likely to have been damaged. I assume the engine control module (ECU) has been damaged, but that is just a guess.
Some specific questions:
- where is the ECU?
- Should I spring for a new one (depending on the ID number), or is one from a junk yard just as good?
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So, I've got a new toy (FORscan ODBII software) and a new code that isn't turning on the CEL (yet) but also didn't show up in OBDWiz either.
P1100 - Mass Air Flow (MAF) Sensor Circuit Intermittent
I cleared it, drove a few miles, checked again and it's set again.
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