DrPepper Posted April 15, 2022 Share Posted April 15, 2022 Hi guys, 聽 I wonder if you're able to help me identify this blue wire under the engine bay? It's a Mk1 Focus 1.8 petrol, almost underneath the battery. Don't know if it's related, but I recently had an O2 sensor warning, followed by battery warning light, also followed by coolant leak 馃ぃ. While checking under the bonnet, I saw this dodgy looking wiring. Was wondering if the coolant from the cracked thermo housing was getting on it.聽 Anyway, in the end the mechanic replaced the thermo housing, and it turned out he didn't even look at the wiring or the battery despite me telling him what I just told you. But I realised that my battery is 6 years old now, so I decided it was probably just on its way out hence the O2 sensor low voltage warning, and for the sake of 拢50 I just replaced it.聽 However....this gnarly looking wire is still bothering me. It looks like it's not only exposed but one of the wires is severed and sticking out.聽 Any ideas?聽 聽 聽 Quote Link to comment Share on other sites More sharing options...
DrPepper Posted April 15, 2022 Author Share Posted April 15, 2022 Wait....don't tell me....it's the O2 sensor, isn't it? 馃槀馃ぃ Quote Link to comment Share on other sites More sharing options...
KenM Posted April 15, 2022 Share Posted April 15, 2022 Looks like you found it Quote Link to comment Share on other sites More sharing options...
KenM Posted April 15, 2022 Share Posted April 15, 2022 New sensor will come with the wiring back to the blue plug Quote Link to comment Share on other sites More sharing options...
DrPepper Posted April 15, 2022 Author Share Posted April 15, 2022 Excellent, thank you. I had watched a few YouTube videos about replacing the O2 sensor, but it was in a different place, which is what confused me.聽 Obviously either a different model, or a different sensor (I know there are two). Quote Link to comment Share on other sites More sharing options...
iantt Posted April 16, 2022 Share Posted April 16, 2022 11 hours ago, DrPepper said: Excellent, thank you. I had watched a few YouTube videos about replacing the O2 sensor, but it was in a different place, which is what confused me.聽 Obviously either a different model, or a different sensor (I know there are two). You answered your own question again . There's 2 . upstream and downstream of the catalytic converter.聽 Downstream is the one that's broke.聽 Part number is 1035595 .聽 https://www.ebay.co.uk/itm/265575169268?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=o28gWE1XQSu&sssrc=2349624&ssuid=&var=&widget_ver=artemis&media=COPY Quote Link to comment Share on other sites More sharing options...
DrPepper Posted April 16, 2022 Author Share Posted April 16, 2022 Excellent stuff, thanks Ian. That's original Ford, plus it's cheaper that EuroCarParts! 聽 Quote Link to comment Share on other sites More sharing options...
DrPepper Posted April 17, 2022 Author Share Posted April 17, 2022 The thing that confuses me about this is....the fault code I got was P0136 "O2 sensor circuit malfunction, bank 1, sensor 2". From what I've read, that's the post-cat sensor. But ...isn't the one pictured above the pre-cat sensor 1? Quote Link to comment Share on other sites More sharing options...
DrPepper Posted April 17, 2022 Author Share Posted April 17, 2022 Ok I've answered my own question again! Bit hopefully it'll be useful in future for anyone else with the same issue.聽 Turns out you can see the cat right there in the photo 馃槀 I was expecting it to be horizontal and further towards the rear. Annoyingly the Haynes manual doesn't have a photo of it! And also, from research, found that green is pre cat, blue is post cat. It's taken me literally days to find that out. Don't understand why Ford went to the trouble to colour code them, but apparently what the colours mean is a secret! Quote Link to comment Share on other sites More sharing options...
mjt Posted April 18, 2022 Share Posted April 18, 2022 Nowadays the cat is generally fitted directly to the exhaust manifold. This helps it warm up quicker (they don't work until they get hot) and also has the benefit it makes it harder for the scum to steal them. Quote Link to comment Share on other sites More sharing options...
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