96 Chevy K1500 transmission stuck in 3rd

[SparkyLU558]

Im having trouble diagnosing the codes my truck is throwing which are: p1886 Shift timing solenoid, p1860 Tcc pwm solenoid circuit - electrical, p1864 4-5 shift solenoid valve control circuit low voltage, as well as p0758 and p0753. The truck ran fine one day and quit the next. When I got in the truck the tachometer, speedometer, and the indicator light for gear selection wasn't working. The transmission is also like its in a failsafe mode and stuck in third gear. Its real sluggish on takeoff and will not shift up or down. Not really sure where to look on this issue. I've read several things about several different sensors that would cause this but im at a standstill right now. I have a brand new pcm that I tried but the same codes came right back and I've also replaced the shift interlock solenoid on the column with no luck.

 

[Schurkey]

4L60E?

Clear all the codes, see what happens.
1. If the trans works normal for awhile, you know it's in limp-home mode now due to the codes.
2. If the codes come back, deal with them then. I suggest downloading the service manual from the links in a thread on this site.

I don't know what a "shift timing solenoid" is. I don't know why there'd be a 4--5 shift solenoid since there is no 5th gear.

And even if the codes suggest shift solenoid problems--and the solenoids are kinda common failures--you can't rule out wire harness issues, or a goofy computer.

 

[tayto]

sounds like another ignition switch.....

 

[SparkyLU558]

4L60E?

Clear all the codes, see what happens.
1. If the trans works normal for awhile, you know it's in limp-home mode now due to the codes.
2. If the codes come back, deal with them then. I suggest downloading the service manual from the links in a thread on this site.

I don't know what a "shift timing solenoid" is. I don't know why there'd be a 4--5 shift solenoid since there is no 5th gear.

And even if the codes suggest shift solenoid problems--and the solenoids are kinda common failures--you can't rule out wire harness issues, or a goofy computer.

Yes Schurkey I believe it's the 4l60e and I've cleared the codes and also unhooked battery to reset the computer. The first three codes came right back afterwards.

 

[SparkyLU558]

4L60E?

Clear all the codes, see what happens.
1. If the trans works normal for awhile, you know it's in limp-home mode now due to the codes.
2. If the codes come back, deal with them then. I suggest downloading the service manual from the links in a thread on this site.

I don't know what a "shift timing solenoid" is. I don't know why there'd be a 4--5 shift solenoid since there is no 5th gear.

And even if the codes suggest shift solenoid problems--and the solenoids are kinda common failures--you can't rule out wire harness issues, or a goofy computer.

Yes Schurkey I believe it's the 4l60e and I've cleared the codes and also unhooked battery to reset the computer. The first three codes came right back afterwards.

sounds like another ignition switch.....

I've read quite a few things online suggesting the ignition switch might be bad. How can I test it to be sure?