I just swapped in a B series into my 93 civic si, i had two codes initially, Cel 10 IAT sensor and 6 Water temp sennsor, upon inspecting i had the IAT swapped with the purge solenoid, no no for me i shoulda known better but i have a modded tuck harness so its hard to tell upon first install, since then i have switched them to the correct sensors and also installed a new water temp sensor, reset battery and same two Cels even before starting the car up. Swapped ecu's, reset battery and still same two CELs pop up upon turning ignition key to on, can anyone tell me whats going on? How would theese still appear even before the car is started after resetting battery and swapping ecu's. Im stumped other than that it runs perfectly

 

IAT sensor is probably fried, they run at a much lower voltage than surrounding sensors, also you may have fried Q31 on the ECU board.

 

you are correct, thats why i replaced the ecu now that the problem is fixed but still the same cels

 

And you replaced the IAT sensor as well?

 

no i did not replace it, i will try that next

 

thahts your problem same thing happened to me ha

 

still doesnt explain the ecu throwing the codes before the car is even started after resetting the ecu, for example the water temp sensor???