shifts to 4 early
shifts to 4 early I have a built trans with a 3000 stall I got everything in and was driving it. Everything was fine then the trans when to shifting in to 4th early so I pulled the DTC and got a P0748 code for the shift solenoid. I also found that the vacuum line had come off not sure how long it has been off. could the vacuum line coming off have caused some damage? I cleared the DTC and it is still shifting early. or am I looking at a wiring issue?
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Joined: Dec 2008
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From: Az
You mentioned a vacuum line comming off. What is that for. 748 is a pressure control soleniod code and would just cause firm shifts. Early shifting is a sign of a bad tps signal or Vehicle speed to the controller.
And early shift could be a TPS or MAF calibration error
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