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Discussion Starter · #1 ·
engine light on and code indicates the heater circuit in the 2nd 02 sensor faulty (the one under the car after the cat). It has two white wires, a grey and a black. I have established that the two white wires are heater circuit. if I unplug sensor and test the two white wires on the sensor with a multimeter it shows no continuity. If i do the same with the other 02 sensor (the one on top on exhaust at front of engine) it shows about 10 ohms. So that seems to verify it needs a new 02 sensor under the car. So i have been having a look but some of them online show the wire colours in the plug in a different order. Mine has the two white next to eachother at one end of plug, but some I see have one of the other wires between the two white ones. This is making me think i need to be very careful to get the right one. are both sensors on the car the same or is the 2nd sensor different spec to first one? can anyone recommend one with a link to it. I don't want to spend more than neccessary but it has got to work. I don't know if people have real problems with the cheap ones. car drives fine, i believe this sensor has no effect on the car, it is just there to monitor effectiveness of cat. but MOT due and light keeps coming back on when turned off. It's my brother's car, he has very little money and I am trying to help him out . Please provide any advice you can. Thanks . (I'm impressed how well this car goes, seems to have a lot more go in it than a Fiesta 1.25 of that era.
 

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Discussion Starter · #3 ·

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In my experience cheap sensors do not last long on Vauxhalls. NTK, NGK, Bosch or Siemens are OEM parts. There was a lot selling that were wired wrong for the Vauxhalls as you seem to have found but by swapping the pins around in the plugs they did work.

Buy cheap buy twice.
 

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Discussion Starter · #5 ·
Hi, thanks for your reply. Do you know if the one before the cat and one after the cat are actually the same spec? there seems to be so many part numbers that the sellers say theirs is compatable with but then some say it is only suitable for pre-cat . I am thinking that did vauxhall have lots of variations of what is actually the same part eg. the cables might all have been slightly different lengths but the sensor the same and then the pattern part makers just do one with the longest cable and say it replaces all of the others? (I need one after the cat which is a fairly short cable)
 

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Pre and post cat sensors are slightly different and not just the wire lengths. The probe ends change as well, pre cat ones tend to have longer probes as they sit further into the exhaust gas flow to get better readings to work with other sensors to set fueling mixture.
 

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I remember a thread about 2 years ago and Marks152 warned of exactly this problem (although it might have been a different sensor) with the cheap off ebay new ones. He had a pic showing that the grey and white wires were completely wrong and wouldn't have a hope of working. As z22se says, the C really demands the proper makes. So many people, even in my 3.5yrs, spend days on the forum writing "it can't be the sensor - a new one was fitted" and yes, it was the new sensor all along.
 

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Discussion Starter · #9 ·
not a question, just giving an update in case it helps anyone else who comes across this.
I bought a NGK sensor. Going by the NGK website they have changed the number of sensors they do and changed the codes for them. Whilst many sensors were the same apart from different length cables on them as far as I can tell, they now do less variants and stick a long cable on them so more are interchangeable with eachother. There's even a video from NGK showing you how to tie up the excess cable with a cable tie
. I don't know if they have also modified the sensor tip to make the reach more suitable for different applications.
If i look up the precat sensor it says use OZA770-EE45 and it says this replaces OZA659-EE70 .
If I look up postcat sensor it says use OZA770-EE45 (the same as precat) and it says it replaces OZA659-EE69 .
So I had a look at prices for OZA770-EE45 but then found if I look for OZA659-EE69 I could get OZA659-EE69 cheaper. People selling off the old stock I assume as that's now sort of obsolete stock number?
Anyway it works, the engine management light stays off and as far as I could tell it was genuine NGK and not a fake (but I wouldn't really know for sure how to tell). Bought from ebay from a UK seller.
 
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