Swap pre-cat and post-cat O2 sensors?

[Burnsie66]

Hi All,

Sorry if this question has been asked before, I did a search and couldn't find anything.

I'm driving a 2003 Holden 1.8 Astra sedan I'm 90% sure my pre-cat O2 sensor is cactus. The post cat sensor looks the same (just with a different length of wire leads). I was thinking that swapping them over might be a way of confirming if it is the pre-cat sensor. My understanding is that the post-cat sensors generally don't die that often, so mine is probably ok.

Can anybody see a problem with this? I don't want to cause more problems, but I figured this would be a good way to check before I shell out for a new sensor.

Thanks,

Paul

[guy 27]

wire lengths are different but iirc.

[Burnsie66]

Yup, thats why I figure they have different part numbers. The post cat one has around a 27cm lead, and the pre cat has one around 75cm, but it gets routed up around the rocker cover to keep it away from the exhaust manifold. In a straight line the shorter one would reach, it just needs to be zip tied away from the manifold. I figure it'd tell me if the existing pre-cat O2 sensor was dead (providing the other one is good), not a long term solution. I'm only worried about whether it's voltage is too high, or whether the computer is going to expect to see more impedance from the longer wires. I don't want to screw things up more than they are already, but I don't want to throw money away either.

[chris_r]

If your O2 sensor is dead, it'd be throwing up an error code of sorts. Buy yourself a cheap code reader like a ELM327 (available in Bluetooth, Wifi and USB versions for Android, iPhone/iPad and PC respectively) and use a suitable app like Torque. It'll give you the voltage readouts from the sensors in question too.

The other and better alternative to the ELM327 is the OP-COM reader. Clones can be bought on the bay of fleas cheap enough and they work well enough (I've had mine for 6 years or so now and used it religiously). The only drawback is that you require a Windows PC for it to work (Win7 or earlier preferred). Best part is, it does everything the ELM327 modules do and more, like immobiliser related functions such as key programming.

[Burnsie66]

In answer to my own question; Yes, you can swap out the O2 sensors, and yes it will get the car out of limp mode and make it drivable. Emission warning light will still come on, but at least I'm mobile again and can go find parts and get to work while I wait for a code reader.

[delemonte]

In answer to my own question; Yes, you can swap out the O2 sensors
Good to know ;)