6th gen ECU
 

I am thinking about swapping the ECU on my '99 LX (f23a1 with my parts car's EX ECU. The reason being it is a more sophisticated computer, either way I want to chip or flash the ECU get what I can out of it. Will the better ECU give me more power, fuel efficiency, and even emissions? I know it will give me better emissions stock, that I could care less here in redneckland, but it may dock me a bit of power (the main source of slight power loss in the f23a4 is obviously the intake and head), gas mileage I don't think there is a big change. Anybody know more than me?

So your EX parts car is a ULEV??

The wiring harness on a ULEV is A LOT different. You'll need to grab the wideband O2 sensor, and rewire the ECU plugs. Pretty sure the pinouts are different in several places. The O2 sensor heaters are powered from different circuits vs. the non-ULEV. etc. etc...

When I posted something similar in your other thread, I didn't realize one was a ULEV. The differences between ULEV vs. non-ULEV are much more than the differences between LX vs. EX.

Your LX has the F23A1 which is the same as the EX non-ULEV car. So you're not gonna gain anything with the "more sophisticated" PCM.

Pretty sure the ex is a ulev, the window stickers are gone but it's way different from mine, knew about the wideband sensor but I had only hoped the harness wasn't different. I'll still look into it it's not a horrible amount of work to adapt the harness. If I see no difference in the ecus I'll just keep it after all my work, bit I'll test it every way I can to find anything. The least I could do with the new ecu is put a monitor on the wideband.

The wiring differences were all documented in detail in the Helm shop manual. I sold that book after we sold that car, so I can't look it up...

if it is an f23a4...
 

if it is a ulev it says it on the valve cover and the engine will be labeled as f23a4