Code P0135 O2 sensor heater circuit

[Orly6]

So I had an O2 sensor wire get melted from coming in contact with the headers, I swapped out the O2 with a new correct sensor & car is still throwing the same code & my AFR aren’t moving like they should they’re stuck at 9.8 (E85) Where should I start looking? Thanks in advance.

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[Mike Pfeifer]

If it was me, I’d start looking at the rest of the harness to make sure it didn’t get damaged as well. The heater circuit is separate from the signal, so it’s possible that further up the harness, the two are melted together somewhere. Does the mustang use the wide band sensors? If so, there are a couple more wires involved. I’m not sure how sensitive the PCM is to shorts, but it’s possible that it may have been damaged from that. But that’s the last thing I would try- in my experience it’s almost never the control unit.

 

[Orly6]

If it was me, I’d start looking at the rest of the harness to make sure it didn’t get damaged as well. The heater circuit is separate from the signal, so it’s possible that further up the harness, the two are melted together somewhere. Does the mustang use the wide band sensors? If so, there are a couple more wires involved. I’m not sure how sensitive the PCM is to shorts, but it’s possible that it may have been damaged from that. But that’s the last thing I would try- in my experience it’s almost never the control unit.

If it was me, I’d start looking at the rest of the harness to make sure it didn’t get damaged as well. The heater circuit is separate from the signal, so it’s possible that further up the harness, the two are melted together somewhere. Does the mustang use the wide band sensors? If so, there are a couple more wires involved. I’m not sure how sensitive the PCM is to shorts, but it’s possible that it may have been damaged from that. But that’s the last thing I would try- in my experience it’s almost never the control unit.

I think I might have found the problem, I’m going to try to splice anything that seems to be pinched & see if that fixes it. thank you!

 

[Mike Pfeifer]

I think I might have found the problem, I’m going to try to splice anything that seems to be pinched & see if that fixes it. thank you!

That looks like a good place to start! Nice detective work!

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