Ok swapped a d15b into my 89 crx si. Changed to the correct P08 ecu. Now before with the stock motor and ecu the check engine light would come on after the car was hot and youd get on it. Well i drove the car with the swap for about 30 miles id say got on it and it came on again. It goes off after the cars turned off but as soon as you get on it the light comes back on. Before with the stock setup i thought it was an O2 sensor but now it has different O2 engine and ECU but seems to be the same problem. Car runs fine vtec still works doesnt seem to be any power loss. Anyone PLEASE???

 

Id go over all the wiring, make sure all the grounds have good connections, temp. sensor, try a different 02 sensor, maybe try a different ECU, or you could always do a code check on the ecu, theres alittle plug above the ecu has 2 wires, hook a button to it, turn the keyforward, watch how many times the check engine light flashes it will go on like pulses, write them down, then getonline and check for the code...May be nothing...thats my 2 sense, hope its some help...

 

did you cehck to see what code it is throwing yet?