I installed a 94 JDM GSR motor in my 93 civic hb dx and the mil comes on for the o2 sensor heater, code 41... The mil doesn't come on right away but only about 10 seconds after the car has been running. I've rewired the o2, replaced the o2 sensor, and even replaced the ecu. I've taken it to 3 different shops and no one can find the problem. I'm open to any suggestions if anycone could please help. I bought a turbo and don't want to put it on until the light turns off

 

Which ECU do you have? OBDI P72, P28 chipped, P30, JDM?

 

i have a p28 chipped

 

You said you tried another ECU? Which ECU did you try? I'm asking all these questions because I too had a code 41. This was on my '96 GSR. I eventually traced the problem to a chip in my stock ECU(OBDIIa P72). It was blown to bits. Took me forever but I eventually found a replacement chip. If you've tried another ECU, then this cannot be your problem. I was just reading a post by someone claiming they had a code 41 & 65, and fixed it by replacing a fuse, first I've heard of that one. You replaced the secondary O2 sensor only yes? If so did you test the resistance across the heater circuit(black wires) prior to installing it? Did you try swapping the primary and secondary sensors?

The problem I'm having is this, with a P28, you shouldn't have a pickup for a 2nd O2 sensor.

 

it's obd 1 so i only have one o2, the post that you read about replacing a fuse, i read that one too, can you find out what fuse this was that was replaced

 

i know the o2 is good because it came off another civic that was running at the time

 

I'd test it with an ohmeter anyway. While you're at it, run wires from the + & - sockets of the plug, and test for battery voltage. The car has to be running obviously hence the wires, which you lead out from underneath the car to test.

I asked which fuse, the fella hasn't responded. I know allot of people have this code, usually related to test pipes on OBDII+ cars. I suspect some have the very same chip shot that was blown in my ECU(Sanken STA335A).

 

Thanks for the help, but still not fixed

 

hehe i have the same problem on customers car del sol h22a and crx minimi setup
both have mil 41 and yes i went follow how diagnose it and i found out both has open hollow cat. on the crx i told him to get that cat fix and he did code 41 disappear. On the h22delslow he just took out the lightbulb. in your case you said that u rewire the harness and still have the problem try restricting your exhaust system

 

check the resistance between the two pins on the o2 sensor which connect to the two black wires. those two black wires are for the heater circuit. check their resitance, it should be between 10-40 ohms.

 

That's the first thing I check. Then I check the connectors and the wiring. If there's nothing wrong with any of that, I try a known good ECU.