Hey guys,

So I got a b18c5 in an em1 with a few bolt-ons (I-H-E) and its throwing me a code for upstream o2 sensor. Well i got the o2 sensor and went to replace it only to see that the previous owner put the downstream o2 in the upstream the problem however is that i cannot find the upstream o2 plug anywhere so i think he may have cut it from the harness because i see lots of splicing. My question is that is it possible to run an upstream o2 to a secondary o2 plug? Or can you just put a downstream o2 in the upstream spot?

Thank you

 

its not a part of engine harness usually.
its in the chasis right abovethe exhaust there should be a hole.

 

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