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[tunnie]

I'm having continuing issues with o2 sensors on my 3.2, these are not the usual 420 codes, but pre cat sensor problems.

On live data, passenger bank looked slow to respond. Was causing EML to come on, so purchased new sensor. It was pattern due to high cost of GM on these, I decided to swap the sensors over to see if problem moved banks.

Problem is after clearing codes & going for a drive, I've got same codes as I did before I moved them! 

Codes I got are: (assuming drivers side is bank 1, thats got the new sensor)

 

[feeutfo]

So, looking at the pic, fault followed the sensor? No?

(Although a different code, it relates the heater circuit?)

If this is the same sensor I got you, it was genuine Bosch, exact same part, just no GM box.

[tunnie]

So, looking at the pic, fault followed the sensor? No?

(Although a different code, it relates the heater circuit?)

If this is the same sensor I got you, it was genuine Bosch, exact same part, just no GM box.

Yes it is 

I fitted it to passenger bank first, then got some second hand ones off Twiglet.

But to me this is saying the new sensor is goosed? 

[tunnie]

Bank 1 is the drivers side right?

[henryd]

Bank 1 is the drivers side right?

Yep 1_3_5 side

[tunnie]

Bank 1 is the drivers side right?

Yep 1_3_5 side

So that has the new sensor, so why is it slow to respond. 

Thinking about it, even with my gadget hands I could not get it super tight as there was just no room. If its not nipped up enough, could that cause it? 

[feeutfo]

It won't warm up as quick if there's an air leak, but then it should see a mixture fault too... But I have no real experience of O2 sensor faults.

See what others say.

[tunnie]

Its getting close to a tunnie bodge & removing the bulb 

[Kevin Wood]

I'd say the sensor is slow to respond because the heater circuit is open.

Worth giving the wiring down to the sensors a thorough inspection, IMHO, including a continuity check back to the pins on the ECU. If the fault is there regardless of the sensor, it's probably not the sensor.

What have the fuel trims been doing?

Does the MAF output look sensible? (12-14kg/h at idle).

[tunnie]

I'd say the sensor is slow to respond because the heater circuit is open.

Worth giving the wiring down to the sensors a thorough inspection, IMHO, including a continuity check back to the pins on the ECU. If the fault is there regardless of the sensor, it's probably not the sensor.

What have the fuel trims been doing?

Does the MAF output look sensible? (12-14kg/h at idle).

That I need to check, does it matter if engine is cold? As i could pop out and check now...

As i removed both sensors, the wiring is entact, nothing broken/damaged as far as I can see.

When you/codes say "Heater Circuit" what exactly does that mean? 

[aaronjb]

Damn, beaten to it by Kev but I was going to say if you've had a heater fault that's still present after a new sensor is fitted then it's well worth belling out the wiring and checking the fuse (if the fuse is separate for each sensor, that is, I haven't looked at the wiring diags).. no heater element could well cause a slow to respond code as well.

[tunnie]

Actually come to think of it the heater is quite weak on the 3.2, giving it large gets some heat. But its no way near as good as my 2.2 for heat, I keep meaning to flush heater matrix.

So heater element? Thats a new one on me? 

[aaronjb]

Heater element in the O2 sensor, nowt to do with the cabin heater

O2 sensors only give an accurate output when they're at a very specific temperature window - this is usually maintained by the gas flow when you're underway and the engine is doing some work, but at light loads and immediately after starting the car (and the 3.2 is generally 'lightly loaded') the ECU turns on a heater element within the O2 sensor to maintain the temperature of the core.

The heater element is essentially a big resistor - the same principle the heater rear screen works on - they get very fragile with age and use so they're easy to brake in an old sensor when removing & refitting it, but generally fairly tough in a new unused sensor (thermal/work hardening of the heater element, I suppose).

They have a fairly beefy power requirement so often have a fuse of their own or a fuse per set of O2 sensors - not sure how it's wired on the Omega.

But the long & short is - if the heater element isn't being fed with power (all the ECU knows is it's 'open circuit' - it assumes it's the sensor at fault but it could be a break anywhere in the wiring to the sensor or the feed fuse) then the O2 sensor will be very slow to respond and the ECU will flag that fault as well.

[tunnie]

Very interesting, thanks for the run through 

Everytime the light has come on, its been shortly after starting, say a few mins max.

Assume this is fused in engine bay? Possible its blown? 

[TheBoy]

If the fault moved with the sensor, thats a reasonable diagnosis. Do you have the PN, in case it was the wrong part (pretty sure the front and rear sensors are different PNs).

Bit worried about the heater faults passenger side.