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Q: Engine swap

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Transmission was working fine from the beginning. But after a engine swap it won't shift into no gear at all. Mechanic said the computer for the tranny have to reset. Is that true?

My car has 200000 miles.
My car has an automatic transmission.

Changing out an engine does not normally require re-flashing any computer module on the vehicle excepting if the owner wants to possibly update the software (if there have been manufacturer updates). What has more likely than not happened is the engine and transmission were re-installed incorrectly and so, for example, the gear shift linkage is not properly adjusted.

It is even "possible" that the torque converter is not attached to the flex plate causing zero oil pressure and thus no shifting. All of the electrical connections should be checked to make sure nothing was left disconnected. If you pull the transmission oil dipstick tube, the fluid level should be at the proper level when the engine is running. If these initial checks do not reveal the issue, YourMechanic can perform a diagnostic on the shifting issue to identify the root issue.

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