420A 1997 RS - Ecu Program

[Nickolision]

Hey guys! Wondering if you guys can help me out, I have a 97’ Eclipse RS so it does have the 420a motor. Car runs and turns on fine, but this engine light is on..
It’s throwing a code for “battery temperature sensor” and when the code was going to be cleared it would just come back. I’ve read that the ECU’s aren’t compatible with early models (1995?) or that they need to be the exact models, years.
I also don’t want to spend $400 to reprogram it at a dealer just for something that isn’t necessary. If someone knows who can program these let me know!
Couple things I’ve done:
• It is another ECU from another car (same model, trim, engine)
• new battery
• coolant temperature sensor already changed 3 times, and still the engine light persists.
• I’ve ran the car for it to learn for 20 minutes, people said that it needs to communicate with the TCM, to measure engine behavior
• idle bounces, from 300-900rpm, I’ve cleaned the IAC, tps, throttle bottle, maybe because of ECU learning?
Thanks you all!!

 

[JeffGS-T97]

The needle bounces on the tachometer rapidly, or slowly? If its rapid i would assume ignition issue. A plug, plug wire, or ignition coil could be misfiring. Pull the plugs and check for unburned gasoline. If you find some, one or more of those parts are failing. Another sign would be choppy acceleration and low engine power like your pulling an anchor down the road.

 

[JeffGS-T97]

One other thing. Don't pull or tighten the plugs while the engine is hot you will completely strip your plug threads on the head and be in for a very tough repair.

 

[dustyboner]

the 95 ecu need to be swapped with another 95

96 and 97 ecus are the same pinouts

98 and 99 are the same also

98 and 99 manual transmission cars can use the ecu from a 98 or 99 automatic.
-- if you use a AT ecu on a MT car, your check engine light will stay on and your redline will drop to 6500 rpms
--you may be able to do the same with the 96-97 but i don't know cause i never had an opportunity to try.

to use the 98-99 ecu on a 96-97 you would have to repin the connector to match the 98-99 pinouts

here are the 96-97 ecu pinouts

98-99 pinouts are HERE

 

[BLACK'98DSM]

I had no idea there was a battery temperarure sensor... I've had the whole car torn down multiple times and never seen anything of the sort.

 

[JeffGS-T97]

I had no idea there was a battery temperarure sensor... I've had the whole car torn down multiple times and never seen anything of the sort.

I'm so glad i wasn't the only person thinking what you just said

 

[dustyboner]

battery temp sensor is built into the ecu. it assumes that the battery and ecu are the same temp since they are in the same area of the engine bay.