00 Silverado. Trans And Ses Light Problem...

[BBC71Nova]

My '00 Silverado 2wd has 148k miles on it. Been driving great like it has from day one. However, yesterday I go out at lunch and all is well. Nothing out of ordinary. When I go to leave work last night the SES light is on. Then as I drive away the tranny doesn't seem to be in 1st gear. I stop the truck, turn it off, back on, etc. Issues remain. Fortunately the trans seemed stuck in 3rd and I don't stop much at all on the trip home so it was driveable. The trip home was enough to confirm that it never leaves 3rd gear and doesn't shift to OD either.

 

After dinner(45min truck likely still a little warm) I decide I'd drive over to auto parts store and pull the codes. Truck drives fine on the trip to parts store. Tranny shifting, etc. SES still on though. Pulling code didn't reveal a lot. I'm suspect of the scan and will do it again with a better scanner from a friend this weekend. Leaving parts store SES is OFF and tranny still working fine. Ran a couple errands and truck continued working great. Park it for the night.

 

This morning jump in to go to work and guess what... SES comes on and stuck in 3rd again. If I stop and manually shift to 1st it will go to 2nd only. Then I can drive off and manually shift to 3rd from 2nd. Truck will not downshift under load either.

 

Has the tranny finally bit the dust? I haven't noticed any slipping or anything. When I get a chance I'm gonna check fluid. BTW, been about 60k since last fluid/filter change.

 

Thoughts???

 

Thanks,

John

[Willshire]

Is the code a P18xx if so it is tranny issue. I'm not sure if 3rd gear is limp mode for the tranny. Sounds like a solenoid problem. Solenoids are inside above the pan and can be tested if you know the reference voltage used to activate the solenoid. This requires a wiring diagram and some voltage info. (Helm manual maybe). Could also have to do with Valve body (worn boost valve) or accumulator. HTH