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Originally Posted by nicmartim
Been fight issues with my 7.3l since I got it and now have reached the end of my rope. The first and most aggravating issue has been happening since I bought the truck. It is a random check engine light that turns on and off at seemingly random times. Codes pulled read P1670 usually and occasionally P1668. I have swapped in 4 IDMs and checked the wiring between the PCM and IDM throughly. The truck has run great up until recently where as now it is dropping the RPM's when the TC unlocks coasting/decelerating from highway speeds. I am thinking the IDM codes are probably not related to the RPM drop issue, but anything is possible.
My question is I have a Phoenix burnt for my PMT1 PCM (DPC-422) and I have read (I think from Cody) that any DPC-422 would work with my chip. Is this correct? I am not concerned about getting the same PMT1 PCM if something else will work with my chip.
If anyone has any ideas and/or suggestions that would be helpful.  I have an AutoEnginuity but currently having laptop issue so unable to do any driving tests. I have tested it thoroughly sitting in the garage idling and things seem ok there from what I can tell. Still trying to learn the AE and all it can do. Thanks!! |
Prepare to be more aggravated.....
I'm not going to go into any diagnostic bits on your P16xx codes because there's no way to pinpoint in what way you should spend your money (and I loathe "throwing parts" at vehicles in hopes that it will resolve a problem).
I will, however, tell you that your RPM drop "problem" is mechanical. It's transmission mechanical. Sorry for the bad news. It's not going to hurt anything, but as you've found out, it's really annoying not having any engine braking. I've found it in two transmissions now (one was my own, the other was one I rebuilt for a guy). The coast clutch snap ring pops out of its groove and you lose much of the clamping force on the frictions and steels.....and they eventually burn up. The only way to fix it is to take the transmission apart. The tuning on the chip doesn't change and I can guarantee that wasting money on another PCM won't fix your transmission problem.