P1607: "mfg controller computer & auxiliary outputs"

I already paid the dealer 90 bucks to check it out, and they said that in order to continue troubleshooting, I'll need to shell-out $700 for a new PCM. And they won't give me a refund on that part if they determine it's not the cause of my troubles.

I'm not so sure I trust this dealer, given the fact that when I had my bogus P0420 code last year, they said I needed to fork over $900 for a new cat converter. Screw that. Cat temperature tested fine, and all I really needed to do was replace a couple of O2 sensors, and no more P0420!)..

Should I take my 99 LX coupe 4cylauto to another mechanic? or should I trust the dealer mechanic on this?


Here is a description of my trouble:

It all started after I got my O2 sensors, and timing belt replaced in another state. Every once in awhile, either while I'm driving, or when I start the engine in cold weather, the ECM/PCM will disable 4th gear, and I'm stuck in 3rd gear and it won't downshift. When this "disabled" mode happens, I'm limited to 3000rpm, the D4 dashboard light turns off, and idle speed is so low that I often stall when stopping at a light. And when I accelerate, it takes forever to pick-up speed (since I'm stuck in 3rd gear).

However, if I start the car again (assuming engine has warmed-up for awhile), vehicle runs without issue (but CEL is still lit). A friend said I should check leaks in hoses that might be playing tricks on the sensors, causing the computer to think it's blown? Thoughts?

 

it's a well known dealer practice to interchange a suspected bad PCM with a known good one to verify the problem.