Car reads 0v from O2 sensor, but sensor works…

[Mitch]

Hey folks, I’m stumped! hoping someone might have some insight.

I’ve got a 2004 Honda civic hybrid (1.3L with a CVT). A while ago my check engine light came on, the pre cat O2 sensor was apparently dead. Took me a while to get around to it but I just recently replaced it, but only to find it was still not reading any voltage!

I have tested the sensor with a multimeter, I get ~0.9 volts when the car is running and warm. I took readings from the car’s side of the connector and the heater supply is fine. The car’s side of where the sensor connects reads ~0.25 fluctuating pretty rapidly around that value. I’ve made absolutely sure there is a good connection between the two. As for past this point, the connector feeds into a larger bundle of wiring that has a hard plastic casing, so I haven’t been able to take a look at anything past that point.

Any ideas on where to go next with trouble shooting? I’ve reset the ECU as well, to no avail. I would have imagined there was a break in the wire somewhere, yet I’m reading some voltage on the car’s side…

Topic

[Rob]

you said its an hybrid… is the car poping up with a check engine light??? because you might not be using the gas engine at the time there fir you will never ready any thing at the o2… alse I would check the wireing and the connectors… is it both o2’s??
you can check the fuses you might have a blow fuse or bad relay… but Im thinging the connector or the wires are bad

[Mitch]

Hi Rob thanks for your reply. The check engine light is on and unlike say a prius, the gas engine is always running is this one, the electrical assist just kicks in when it can so the engine doesn’t have to rev up as high.

I haven’t checked fuses or relays aside from the ECU, but I don’t see where else it would connect to?

Do you or anyone else know how I can go about checking the wiring inside the car?

[Shaun Flichel]

Check to be sure the engine grounds are solid. Then work your way back. If it’s not getting to the ecm. Split the circuit in half. Which means to test it half way down. Then go from there

[Dave Tidman]

There are a slew of O2 codes, it would help to know which one it is.

If you have a scan tool with data pids, I would check the O2 function first, that will tell you what the ECU thinks it is getting. If the ECU looks like the sensor is dead, then you will need a wiring diagram and you will need to chase if from there.

A quick check of fuses would not hurt.

[Author]

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