dabatman99
New Member
My civic is a standard transmission. I've been having issues with the Primary O2 sensor (had a P0135 O2 heater circuit code initially). I know that the 04 and 05 civics have a wideband O2 sensor, and I replaced it with the correct Denso sensor. Still not working. Upon further investigation, the relay that activates the Heater circuit for the sensor was not turning on. I found that there was no ground to the relay coil (the wire comes directly from the ecu and I verified continuity). I tried jumping it to ground and the relay would work. However, the O2 sensor would not work correctly until I disconnected the temporary ground wire, and then it see the sensor would respond a bit then go back to a high value and stay there. I'm thinking there might be something going on with the ECU and pulled it out and found that the one in there is a 37820-PLM-C08. I looked online and every one I found was saying it's for an auto transmission (you can see the pins in where the "C" plug would go). I don't know what model of ECU I can get. I know I will have to get it flashed at the dealer, and I'm ok with that, but I don't want to buy a new one through the dealer, and I don't want to buy one online that won't work either. Help please!