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I picked up a 1995 K1500 this weekend with a 5.7 tbi, 4L60E trans and a 7427 PCM
It has a problem with the trans/PCM interface. It will operate in 1-2 gear but will not shift any higher. If you pull the fuse it will shift to 3rd and stay there.
PO stated that these problems started after a break in and some work on replacing the whole dash assy and he thinks they pinched a wire.
Any diagnostic work I need to do right away?
The link to the gearhead-efi '7427 information, including wiring diagrams: http://www.gearhead-efi.com/Fuel-Inj...Information-0D
dave w
When the key is on accy I have a gear indicator light but when the key is turned to run the light goes out. I think this light is tied to trans shifting somehow.
I would check power to the gear indicator. If its lit in accessory, it should be lit in run. Worn or out of adjustment ignition switch? You are going to have to do some tracing with a test light, Check engine light illuminated? Have you tried to pull diagnostic codes?
Is this transmission the original? Sounds like an issue I had someone bring to me before when they put a 97 4L60E in the truck and it didnt work out. It would show in the codes for the transmission though; I believe there were no less than 3 different reasons for the 3-4 lock and vise-versa in troubleshooting section of factory repair OBD1 4L60E manuals.
Pull codes, post here. If there are no codes start checking cables and if transmission is changed.