New member 03 Orange Svt electrical issue

[nate4027]

Hey guys I need your help. I had a faulty upstream O2 sensor and went to replace it only to find two wires that come off the plug on the harness side that were cut and appeared to have been disconnected for sometime. One is black and the other is yellow/black. Any clue what these two wires are for? I was unable to find electrical diagrams so thats why I eneded up here.

[BC_ZX3]

Upstream O2 sensor is on the right in the pic. Yellow/black is part of the 02 heater circuit. Not sure what the black is for unless it's been spliced in for Green/yellow.

Wiring is for an 02 SVT, although non-SVT is identical.

[nate4027]

Ill check it out. Not sure what the O2 heater circuit does. Being disconnected it doesn't throw any codes.

[BC_ZX3]

Originally Posted by nate4027

Not sure what the O2 heater circuit does.

Exactly what it sounds like. It preheats the 02 sensor. O2 sensors, like catalytic converters, need to be up to temperature quickly to work most efficiently.

It should throw a code unless your SVT has a custom tune in place.


P0135 - HO2S Sensor Circuit Malfunction (HO2S-11)
During testing the HO2S Heaters are checked for opens/shorts and excessive current draw. The test fails when current draw exceeds a calibrated limit and/or an open or short is detected.
Causes:
Short to VPWR in harness or HO2S.
Water in harness connector.
Open VPWR circuit.
Open GND circuit.
Low battery voltage.
Corrosion or poor mating terminals and wiring
Damaged HO2S heater.

[nate4027]

That makes sense. Now the question is I can't find where these two wires connect in the harness. I see that they run across the top of the cooling fans to that passenger side but they just dangle from there.

[nate4027]

Does anyone know where the two wires that run off the upstream 02 sensor connect to? I'm getting a P0136 and P0141 codes. The 136 code doesn't make any sense due to both 02 sensors being brand new. Not saying the could be bad from the factory but they are Bosch sensors.

[BC_ZX3]

Green/yellow goes to fuse 18 in the Battery Junction Box.
Yellow/black goes to pin 93 of the PCM.

Bosch sensors have a bad reputation on FF.