The Automatic Transmission (A/T) learned values must be reset anytime the transmission or valve body has been replaced. Failure to reset A/T learned values can result in harsh or soft and flaring shifts.
Up until about 2005, the A/T learned values on most Mitsubishi vehicles was part of the ECU’s volatile memory. This simply means that if the power to the transmission ECU is interrupted, the learned values will be lost. Some ECUs use a capacitor to allow the system memory to retained for a short while. This is why on some vehicles simply disconnecting the battery or pulling the ECU fuse will not clear the memory. On these types, we not only disconnect the battery, but we also have to hold the cables together for about one minute to discharge a capacitor in the ECU that acts something like a battery.
Finally, there is a third type that was used on late model Mitsubishis. On these, a scan tool must be used to clear the A/T learned values. Disconnecting the battery and holding the cable together will not work. Failure to clear the A/T learned values can result in extraordinarily long drive times to try and get the ECU to relearn.
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