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Have a 97 Gm Pickup, and access to scan tool. 4L80E Trans. has 2nd gear and reverse only.The trans.starts in 2nd gear and will not shift higher or lower.Changed the ignition switch/wiring harness assembly,no difference.TPS checks out OK.....and what happened after this is puzzling.
I went under the truck and disconnected the large round multi-pin wiring harness at left rear of transmission,re-connected it, test drove the truck and trans. started in 1st and went through all the shifts normally and to O.D. Thought I had it, but after a few blocks it went back to 2nd gear only.Tried disconnect and connect again of harness,shifted Ok for a few blocks... and then back to 2nd gear only again.
This is definetely an electrical problem.From the beginning we have noticed the orange engine service light does not come on every time the key is switched from off to on... and it should. Gm trans. Tech told me the ECM for those model years are not a problem. Has anyone encountered this type of trans.issue with the 4L80E?
Den |