Join Date: Oct 2016
Location: Savannah, GA
Drives: 1988 Mazda B2200 w/ FE3 from 2002 Sportage
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I did indeed have pin 72 on the ECM ran to ground. I took that off and the AT/MT coding fault went away.
As far as the IAC, it was a P1505 code. It doesn't matter much as I had already checked all 3 wires for the IAC and again, everything checked out fine. I cleared the codes, drove it around a bit, and it seems to have stayed gone. I will check the codes again tomorrow after work once it's had a chance to drive on the highway.
I pulled the dust cover off over the no 1 spark plug and hooked my timing light's ammeter around the plug lead. I had to set it to "2 cycle" for it to read the RPM correctly, but it does read 820 RPM. It fluctuates some, but nothing bad. It still sounds like a rough idle to me, but the RPM is correct so I'll just keep it as is.
I do have one other question that maybe someone can help me out with. ECM pin 46 is connected to the ground side of the AC relay. When the AC gets turned on (or at least when the ground for the relay is provided by the AC switch), does the ECM step up the engine RPM or is it only a signal to tell the ECM the AC is turned on so that it can monitor the coolant temp for the AC cutoff relay? I added AC to my truck but I don't have that pin populated on the ECM plug (I probably ripped it out when I cleaned up the harness) so I haven't connected the AC relay to the ECM. When I turn the AC on the engine nearly stalls before recovering and the RPM drops some. I just want to know if it's worth bothering to pull another harness when one becomes available at the pull-it yard (or pull an ECM pin from the 97 model in the yard and just add it in).