SES illuminated P1800 Max shift code

[inition]

My 1999 Olds 88's check engine light popped on last week. It was the first time driving my winter car after letting it sit all summer.

The transmission rarely shifts hard or acts up in any way. From my google research, the code is thrown when the trans takes longer then .65 seconds to shift.

Currently, the car is running great. The fluid is full and looks nice and clear on the stick. I last changed the fluid at 150k miles, currently at 170k miles. When I say changed fluid, I dropped the pan, replaced the filter and filled it back up.

Should I replace the PCM or keep driving it till I need a transmission rebuild?

Thanks!

[Oldman]

I'd assume that sitting all summer is the reason for the problem. I'd erase the code and not worry unless you see it again. I'm not sure if you have the same transmission as the Bonnevilles have, but most of us have installed shift kits to help with the slow shift problems. There's a couple you can purchase and a couple that simply require some small pieces of tubing for spacers in the valve body. If you have the same transmission as a Bonneville, sear "shift" on this site and you should see quite a few posts describing the process. It's only a little more involved that the transmission fluid change that you already performed.