I have a 2002 lancer oz it has a MIL on and the code is warm up catalyst below threshold. I tested the o2 sensor and it is working exactly how it should. There should be 9-11v at pin 3 on the A/T ecu at idle I have that but when you rev the engine your supposed to have 9-11v momentarily and then it should jump up to source voltage, or what ever the alternator is putting out and it will not go above 11v.
Between pin 41 and pin 3 there should be 4.5-8 ohms and I have 10 ohms between the two pins should I declare the ecu the problem, or could it be something else. power and ground to ecu is good.

 

is ur cat still good?

 

Just curious, are you on the OEM battery?

 

what's the code? it's probably the cat and not the ECU.

 

was their a recall for this?

 

there was a recall for a ECU flash on the 02-03s but i do not remember the exact reason. when i bought mine i noticed a sticker saying the flash had been done.