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420A 1997 Eclipse 420a motor need PCM help

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Probationary Member
Nov 7, 2022
Wilkesboro, North_Carolina
So I have a 1997 Eclipse 2.0 and I have changed the wire harness to a 1998 harness, every ECM I try in it won't work. Would i need to reprogram the ECM being the motor is a 1997 and the pc is a 98?

Note they are both 2.0 automatic 420a non-turbos
As minute as the year is I think it's just best to have it tweaked to the specific year. It is always the smallest things that make your car not want to run. I'm a fan of doing things myself but take it to an electrician and see what they say.
I think the main difference between 97 and 98 is the evap system. Even with a difference there, the engine should still start & run so I think you've got a bigger issue.
yea it wont start and the car seems to always do something new sometimes ill have spark sometimes i wont but i have tried everything i can think of besides getting the pc programmed
I have a 1997 Eclipse 420a automatic. The motor harness has been swapped to a 98 along with the ECU that matched the harness.

I'm at a loss ATM because it will fire on 2 cylinders sometimes but will not start.

Does anyone know if you would have to program the ECU being its a year up. I have also been told the 420a ECU is locked?
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The ECU is indeed locked, and is exclusively programmable by a software used only by the manufacturers. Regardless, the 97 & 98 have an identical ignition system. If you're lacking spark it isn't because the ECU needs to be reprogrammed. Have you checked for signal from the crankshaft position sensor?
I've never heard of an ecu needing to be programmed for any of our cars. there is no anti theft system, the ecu may be coded to a different vin number in its memory, but as far as the ecu knows its still plugged into the vehicle with that vin number. there is no coded key or chip in the key for our cars, or anything to tell the ecu its not in the original car. edit i searched and confirmed you do not need to reprogram a new ecu from car to car

why do you think the car needs a new ecu? im more inclined to say there is another mechanical issue. it sounds like the timing is off on the motor. have you verified the timing belt and timing marks are all lined up correctly? have you done a compression test? how do you know the 98 motor is good?
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