O2 sensor wiring question (1 Viewer)

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Aug 4, 2008
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Location
Saint Augustine, FL
I have been battling a persistent rough idle for some time and now have an O2 sensor CEL - sensor #1. I replaced the old sensors with new OEM and the code is still there. The wiring on sensor #1 is a custom job done by a PO that I can't make sense of - 6 wires in the harness instead of 4, with some of them joined together (PO deleted the factory harness connector). SMH

I found this handy diagram in the FSM that makes the wiring clearer, but doesn't explain which color wire from the sensor goes where. The FSM does clearly identifies the location of each of these (OX1, OX2, HT1, HT2, +B, and E1) at the ECU.
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The sensor has four wires - two black, one each of white and blue. None of the wires have continuity with each other. The white wire has continuity with the body of the sensor.
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Any ideas? Has anyone dealt with this before?
 
Well the wiring diagram shows the two wires for the heater should have some continuity. The FSM says between +B and HT1/2 there should be 5.1 to 6.3 ohms of resistance. I would say the heater are the two black wires, but I don't really know.
 
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Since the white wire has has continuity with the sensor, and your diagram shows E1 is grounded, then I would guess the white wire is E1. That would leave the blue wire being OX1/2. I found the table below in the 3Fe engine manual.

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Great catch, mbb. I was wrong - there is continuity between the two black wires, so I think you're spot on about them being the heater circuit. And I agree about the other wires as well. Any thoughts on the dotted lines in the wiring diagram? I'm really scratching my head on that one.
 
I think it indicates the O2 wires are shielded. I suppose it could be embedded in the blue insulation, but more likely there is shielding around the blue wire as it runs though the bundle casing.
 

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