O2 sensor heater wire, how to test?

[240z4u]

Well, my car has been running rough during light throttle and idle. I hooked up my laptop and found it was running WAY lean. I figured out it was the O2 heater starting to cool off at idle and low load situations.

I have 12v on one side, and no ground on the other. I probed at the harness, and probed at the ecu (went off the FSM for the right wire). Still no dice.

The O2 heater is on whenever the key is turned on correct? If something is out of wack with my power FC I may wire a relay to the ground side and trigger the o2 sensor ground from a key-on source.

I RARELY sit with my car off and key turned on, so I am not worried about shorting the life of the sensor. Anyone have any other reasons it would not work?

Thanks - Evan

[mott6904]

The o2 sensor has power and then computer grounds it out. Have you check continuity for that wire to make sure you dont have a short first?

[240z4u]

Thanks for pointing out the obvious, duh for me LOL.

Ill check that tonight.

Evan

[gawdzilla]

pretty sure it doesn't ground through the ECU. if you look at the wiring diagram, it gets ign 12v (already fused), and grounds through the rest of the body grounds. just wire it up that way and it should heat. its just a simple resistor heating element.

as an aside, the o2 sensor should still work without being heated. it will just take longer to get to operating temp

[240z4u]

The O2 does ground through the ECU. I know that for sure, thats how the diagram in the FSM shows it. Thats good to know I can just do an IGN source and ground though.

The o2 sensor does work fine at higher EGTs such as cruising, but at idle I can watch the AF go lean as it slowly cools off. I have it mounted about 10" downstream of the turbo. It is possible that the sensor is dying too I suppose. I do have a spare, so thats nice.

Thanks guys, Evan

[gawdzilla]

took a look at the 26 and it doesnt go through the ecu. on the 25 it does so you're right. either way its just a resistor so if you're not getting a ground through that pin then i'd just ground it to the body

[240z4u]

Ill do that tonight. Thanks man.

Any thoughts as to the fuse size I should put on the wire?

Gawdzilla, thanks for your help. You always offer good info.

Evan

[gawdzilla]

Any thoughts as to the fuse size I should put on the wire?

no need. take the source from ign so its already fused and wire it up. that's how it is stock.

you still heading to DNIdrags? i wrecked my car pretty bad on the track this past weekend. body looks like crap but the frame seems ok and the car still drives true. i'm probably not heading out there anymore and saving money for some overfenders/body work

[240z4u]

Yeah, im still going. Sorry to hear about your car man.

What happened??

Evan

[gawdzilla]

was just being a noob at learning drifting and trying to slide a car without a smooth power band basically. car came out way late and on a narrow part of the track. went all the way around and slid through some frozen grass/snow. had to wait for the concrete wall to stop me

[240z4u]

Ouch, well there is always next year!

Evan