Testing 02 sensors?

[knockoutgiant]

Afternoon guys.

I've had a CEL on for about 2 weeks now, just got around to using a scan tool on it. Scan tool says something along the lines of "02 Heater circuit volts low. Bank 1 Sensor 1."

Main questions are:

1) This is the first sensor on the downpipe (Right up near the turbo)

2) How exactly am I supposed to test to confirm this fault?

I have tested for resistance on the two black wires on the 02 connector, reading about 3.4 Ohms (Unsure what it's supposed to be reading?) and also checked I'm getting 12V from the wring loom connector. Any help would be greatly appreciated!

[Rosssub]

On BE/BH rev D/E that code is referring to this O2, in the left bank header:

If your car (BE/BH/BL/BP?) doesn't have one there then it is the one in the DP.

I think the scan tool is confirming it, the pre-heater is gone.

[knockoutgiant]

Ugh, knew I'd forgotten something ahaha.

03 BL5 Manual.

I want to test the sensor to make sure. I don't want to be like all the other guys at work that say "This is the problem, lets replace it" then they replace it and it doesn't fix the problem *rolls eyes*

I would have thought if the pre-heater had gone I wouldn't be getting any resistance back?

[Andy_Mac]

Don't think it'll be pre heater. Mine doesn't show up at all until warmed up. Always assumed the pre heater was gone in mine as i can see it read nothing for ages when logging it and finally comes right after the exhaust has got it up to temp and then reads perfectly, never any codes. Unless mine is something completely different. Get romraider running and it should be able to confirm.

Ross is the one in that pic used for afr or cat stuff?

Does yours have the secondary air pump thing? Or is there still a cat in the uppipe? Can't remember what year they came in.

[Andy_Mac]

Just did some logging of mine whilst idling. Logger shows it stuck at 14.7afr and 255 ohm before its warmed up, not sure if thats a real reading for resistance or just the limit for the reading. And once its started working, 2-5 mins after the cold light goes out, it stays at 14.7 and gives 33 ohm. Resistance drops as afr drops.

[Rosssub]

Andy the one pictured is the BE/BH rev A/B/C o2 sensor (they only have one, nothing in DP). It's not the exhaust bringing your O2 up to temp, it's the O2 heater. Idle exhaust isn't hot enough for the O2 to read properly. A failed O2 heater will give fault code P0031 or P0032.

Knockout, with the O2 heater getting 12v you know the relay and fuses are ok. The ECU earths the O2 heater to turn it on. With the ignition on/engine off the O2 sensor should heat up, hot within minutes.

The O2 heater power feed will show 12v, the O2 heater earth (ECU heater signal) should show 1.0v when idling.

With ignition off, resistance between heater terminals at the sensor should be 10ohms, any less replace the sensor. More than 10ohms shows a wiring fault or short.

Edited April 6, 2015 by Rosssub

[Andy_Mac]

Ah sweet. Maybe mine is alright then. Could take more than 10 mins some days, isn't that to long? Tuner thought is was faulty too.

Would have thought they needed to read accurately at idle to get afr right since its closed loop.

[Rosssub]

AFAIK will only go into closed loop once coolant temp sensor shows normal operating temp. Anything under that will be pre-set cold run fuelling.

[knockoutgiant]

 Rosssub said:

Knockout, with the O2 heater getting 12v you know the relay and fuses are ok. The ECU earths the O2 heater to turn it on. With the ignition on/engine off the O2 sensor should heat up, hot within minutes.

The O2 heater power feed will show 12v, the O2 heater earth (ECU heater signal) should show 1.0v when idling.

With ignition off, resistance between heater terminals at the sensor should be 10ohms, any less replace the sensor. More than 10ohms shows a wiring fault or short.

Exactly what I was looking for! So clearly the 3.4 Ohms I've got is far too low and needs to be replaced right?

How do I check the earth? Obviously get the car idling, switch the multimeter to volts then probe which wires?

[Rosssub]

One black wire is the power feed, the other is the ECU heater signal (earth). If you see less than 1.0v when idling through the heater signal wire, you will need an ECU pinout for your car to find the signal wire/pin at the ECU. Then check the signal voltage at the ECU end. If less than 1.0v, then find the ECU's main earth pin/wire and check resistance between the ECU earth and chassis. If it shows more than 5ohms the ECU has a bad earth.

But that will cause a lot more issues than just a code P0031. CEL P0032 (high voltage) is when the ECU sees more than 8.0v through the signal wire.

In both cases the most likely scenario is a dead O2 pre heater.

[knockoutgiant]

So I probe the wire at the connecter and at the ECU to get the 1V reading? It takes me a little while to get these concepts into me head, electricity's really not my thing ahaha.

Damn expensive sensor too! Repco decided they wanted to charge me $950 *Rolls eyes*

Went to an auto sparky, he can get me one for $330. He also said the Resistance on this specific sensor should be 2 Ohms?

[Rosssub]

Was that plugged in, ignition off or unplugged? Partsouq for the win, under $200 delivered for a genuine one:

https://partsouq.com/en/search/search?q=+22641AA180+

[knockoutgiant]

Actually that's the wrong part number, part I'm after is a 22641-AA220 which they're showing no stock of.

I'm unsure to be honest. I assume he's meaning unplugged

[knockoutgiant]

Okay so, I removed the sensor, applied 12V to the black wires. It got hot, working properly? Also got a rag with meths on it, smothered the end to get a reading and I got 0.8V. Surely that's enough? Which leads me to the question why am I getting the check engine light?!

[Rosssub]

P0031 O2 sensor 1 heater low voltage

P0032 O2 sensor 1 heater high voltage

P1130 O2 sensor 1 heater open circuit

P1131 O2 sensor 1 heater short circuit

P1134 O2 sensor 1 AFR micro computer problem

P0171 system lean

P0172 system rich

It might not be getting hot enough, or taking too long to get hot. Your ECU knows due to the voltage it sees through the signal wire.

P1130 or P1131 I would say check the heater wiring circuit.

P0031 or P0032 I would say the sensors heater is stuffed.

Any of the other codes would point towards the O2 readings being off, not the heater.

[knockoutgiant]

I'm going to go with if taking too long to heat up, it did seem to take a little while on the bench. I'll get another one on the way so I know. It's really starting to annoy me now aha.