Have an 02 Expedition that I just changed both pre-cat sensors in. The old sensors weren't throwing codes but it has about 95k on it so I just replaced them. First drive after the new sensors were installed it throws codes saying that the heating circuit is bad for bank 1 sensor 1 and bank 2 sensor 1. Can't remember the code numbers at the moment. Read on here that it could be a problem with the wiring, so I wanted to rule that out before I go anywhere else with the repairs. Can anyone tell me what wire colors at the sensor connectors do what? If I understand right there are a power and ground for the heating circuit and a power and signal wire to make four wires, correct? Just need to know which is which? Thanks.

Steve

 

A better question would be: "What did you use for replacement parts?" since you introduced new faults into the system along with the new parts.

 

First thing I thought too, but I want to rule out any other issue before i shell out another $100 for another set of sensors.

Steve

 

interested in what you find out. i put all new 02 sensors in my 99 expy. i put in bosch sensors. i am also getting a heater circuit fault on bank 1 and bank 2. i pulled up my live data and watched the 02 sensors and they seem to be operating normally. i haven't started to really dig into the problem yet though.

 

So, are you actually going to answer the question that was asked?

 

Sorry about that. They are Standard Motor Products O2 sensors. I had used them before with no issues so I got them for the Expedition. Maybe should have just bought Motorcraft or Bosch I guess.

Steve

 

Which part number.....? Generics or vehicle-specific?

 

The Standard part # is SG459. They are supposed to be vehicle specific. Got them from Rockauto and they are listed as upstream sensors for an 02 Expy with a 5.4, which is what I have.

Steve

 

So, are these generic O2 sensors that you spliced into the original harness?

If so, which color wires on the O2 sensor does the instructions state is the heater circuit and which color wires on the O2 sensor are the for the sensor signal?

(The original Ford harness uses the Red/yellow stripe to provide vehicle power to the O2 heater circuit and Grey/Red stripe provides the ground for the O2 sensor signal.)

 

On the sensor's attached harness, there are usually two wires that are the same color. Those are the heater wires. Verify that one them is mated to each of the vehicle harness wires that Jim supplied.

Unplug the sensor and measure the resistance of the heater. The PCM is expecting a value between 3 and 30 ohms.

Check for internal short-circuit between the heater leads and the sensor body and both of the sensor leads.

 

Below is the wiring diagram for 97-00, which may or may not be the same as your 02. You'll have to see if the colors are the same or not. The sensor numbers shown are (bank, sensor). Meaning #11 is bank one sensor one. Bank one is the passenger side of the vehicle.

 

Just been trying to get time to check things out with the O2 sensors. I appreciate the info. As soon as I get the checks that were suggested done I will let everyone know what the verdict was. Hopefully in the next day or two.

Steve