My Disco is not reading either front O2 sensor.

Long story short, at some point the front O2 sensors were rewired by somebody. The previous owner was never able to figure out the problem and sold it out of frustration.

I've tried every solution I've found on here to see if it's a short in the 'T' bracket, faulty sensors, etc.

No other codes are thrown other then no signal from the front O2 sensors.

I've decided to rewire the sensors so I at least know it is correctly connected to the computer.

However, the wire colors on the Disco side of the O2 connectors do not match the wire colors of the computer connector C0635.

I've looked at the RAVE manual and can't quite verify via the labeling, what wire goes where.

I'm also confused about the 2 heater wires on each O2 sensor. Do both heater wires get 12v, or is one heater wire positive and the other ground and they are interchangeable?

To make it easy, let's say the wiring on the actual sensors is this:
LEFT
1 - Black (Signal)
2 - Grey (Ground)
3 - White (Heater)
4 - White (Heater)

RIGHT
5 - Black (Signal)
6 - Grey (Ground)
7 - White (Heater)
8 - White (Heater)

And according to the RAVE, C0635 wiring is this:
1 HO2S heater RH bank - downstream
2 Not used
3 Not used
4 Not used
5 Thermostat monitoring sensor
6 Not used
7 HO2S heater LH bank - downstream
8 HO2S sensor RH bank - downstream
9 HO2S sensor LH bank - upstream
10 HO2S sensor RH bank - upstream
11 HO2S sensor LH bank - downstream
12 Not used
13 HO2S heater RH bank - upstream
14 HO2S sensor RH bank - downstream
15 HO2S sensor LH bank - upstream
16 HO2S sensor RH bank - upstream
17 HO2S sensor LH bank - downstream
18 Fuel pump relay
19 HO2S heater LH bank - upstream
20 Not used
21 Thermostat monitoring sensor
22 Not used
23 Main relay
24 EVAP system leak detection pump motor (NAS vehicles with positive pressure type, EVAP system leak detection capability only)


Could someone please explain to me with a simple listing of O2 sensor PIN number to C0635 PIN number?

Thanks!

 

Each of the heated oxygen sensors have a four pin connector with the following wiring details:
-Sensor signal ground (grey wire – connects to engine management ECM)
-Sensor signal (black wire – connects to engine management ECM)
-Heater drive (white wire – connects to engine management ECM)
-Heater supply (white wire – connects to fuse 2, underbonnet fuse box)



Heater supply (white)- Left 4 and Right 8 go to number 2 fuse under hood

Heater drive (white)- Left 3 goes to pin 19; right 7 goes to pin 13

Sensor signal (black)- Left 1 goes to pin 15; right 5 goes to pin 16

Sensor Ground (grey)- Left 2 goes to pin 9; right 6 goes to pin 10


I hope I put this in a way you can understand. If you have any questions I'll try and answer them for you. This is where I got my info>>>From the RAVE>>>O2 sensor info..pdf

 

Man, Jared that's perfect. Thank you.

 

You're welcome. Report back to us and let us know if you got the problem solved.

(It is important not to confuse the sensor signal pins; the signal pins are gold plated, whilst the heater supply pins are tinned,
mixing them up will cause contamination and adversely affect system performance.)