My mechanic has been trying to solve a P0443 (Evap Purge Valve) fault code on my 2003 Ranger, 3.0 EFL and so far has been unsuccessful. I would generally consider him to be a good mechanic, but he's really dropped the ball on this one. It's been in the shop 6 times now and still isn't fixed. He's changed the purge valve (twice) the evap valve (twice) and the fuel tank pressure sensor. He's rewired most of it. He's run smoke tests and pressure tests. I've changed the gas cap. Now he is telling me the problem is in the PCM/ECU. I have my doubts.

Being very good with computers and electronics (mechanics, not so much) I pulled the ECU, and tracked down the transistor that drives the purge valve. It tests good. I hooked up 2 LEDs to the wires for the purge valve (pin 56) and the vent valve (pin 67) and duct taped them onto the hood so I could watch them as I drive around. The lights go on and off to power the valves pretty much as expected, based on this article. Likewise while monitoring the tank pressure via OBDII and Torque, it seems to be as expected. I went ahead and replaced the transistor (MJD112G 2A 100V Bipolar Darlington) anyway and reflowed the solder on the connector and all related components.

So my first question is: Do any of you think it really is the PCM/ECU, and just what might be wrong with it? Or should I tell my mechanic to keep looking elsewhere. Where?

Next question is: I will probably end up buying a refurbished/reprogrammed PCM from fleaBay for approx $125-$150. My PCM is a part number 2L5A-12A650-CC MP2-111. I've noticed that many of the refurb'ed PCMs come with 2 new PATS keys, but the listings I've found for mine do not. So does my particular vehicle keep the PATS codes stored elsewhere? Or will I also need new keys?