More PCM Questions

Along with my temp. guage not working, as I discussed in a post last week, my check engine light came on. It produced code P0128, Coolant Temp Below Thermostat Regulating Temperature. I'll be replacing that tonight, but don't belive it is the problem. I continue to have good heat and the car warms up in its normal time frame. My parts guy said a bad thermostat can cause the car to behvae oddly.

I'm still concerned my problem is related to the PCM or wiring to it. I put my electrical meter in circuit to check for current. With the key on, I don't see any current. Does the car need to be running? If I'm not getting current, does that confirm it is either wiring or PCM problem.

Finally yesterday afternoon, the transmission would clunk when I put it into gear and when it shifted while accelerating. There is no clunk when the car downshifts. The problem seem to be slightly less this morning, but has returned to its position yesterday. Could this be related to something with the PCM, or is this a new problem for me?

I've had really good luck with my Alero and have 187,000 on it. But I'm concerned I may be on my way down. Any thoughts or other stories of high milleage Aleros?

On your suspected PCM problem, the only thing I can recommend is run voltage checks and continuity (resistance) of the wiring. Checking current is very difficult in those circuits and you do not want to damage the PCM or any other electrical components. You'll probably will need GM Alero wiring diagrams for wiring color coding and pin outs.

The tranny problem could be related to he PCM since the PCM controls line pressure and all the solenoids (shifting) associated with the valve body but it is hard to say.

I agree with the PCM issue that Bob stated. Thats the best way.