Heated 02 sensor
QI have a 2007 Vauxhall Astra H 1.6 16v. I purchased it a few months ago to do a few repairs on it and intend to use it as a work car. It runs/drives fine. One of the problems I have is with constant pending fault codes P0136 and P0141 relating to the sensor after the cat, Bank 1 sensor 2. They remain pending and then change to current codes after a while, when deleted come back after a short time.
I have a Draper scanner that gives me live data that I can put into graph form. The first sensor (sensor 1 bank 1) constantly switches voltage as it should, the second sensor with which I’m getting the error codes for appears to operate fine, the readings are what I would expect and remain pretty constant with slight changes during throttle and decrease throttle. I purchased a new sensor from ebay and fitted it but still get the same codes. I then noticed the wire colours on the new sensor were not the same as the sensor I removed, the new sensor had white wires in pin 1 and 2, grey in 3 and black in 4. My original sensor (if it is correct) has pin 1 grey, pin 2 white, pin 3 black and pin 4 white. Is black signal to the ECU and grey earth to the ECU?
After noticing this I popped out the pins in the ebay sensor and put them into the same position as the original sensor, so the colours matched the same pins. Still the same two error codes are present P0136 and P0141.
I can’t seem to find a wiring diagram for the heated circuit for bank 1 sensor 2. I believe that the two white wires are for the heated element part of the sensor?
What I would like to know is where the two white wires go to from the plug at the sensor, if they go to one of the two plugs at the ECU and what two pin numbers they go to at the ECU. Should one of those white wires have 12V constantly or is there only 12V when the ECU allows it? Is the other white wire a constant earth or does it switch in the ECU to make it earth? If I check for 12V and it’s present at one of the white wires can I just run a new earth wire or does it have to go through the ECU?
If it turns out to be an ECU issue would it be possible to link the second sensor heating wires to the first sensor or would the ECU still detect a fault.
My Lambda plug wiring is: Pin 1 brown/green Pin 1 White Pin 2 Brown/black Pin 2 Black Pin 3 Red/blue Pin 3 White Pin 4 Green Pin 4 Grey
Any help really appreciated.
James Fraser
AAutodata gives the code descriptions as follows: P0136 Heated oxygen sensor (HO2S)2, bank 1 - circuit malfunction. P0141 Heated oxygen sensor (HO2S) 2, bank 1, heater control - circuit malfunction. This is indicating that both the heater element and the sensor in the unit have a circuit problem and could well be pointing to a wiring fault.
As these code were present before the replacement of the sensor, I suspect that the sensor is not the root cause and the problem may be a break in the loom or a poor connection at some point.
The wires from the Lambda plug should be connected as follows:
The Brown/green wire (terminal 1) connects to terminal 19 on the ECM, the Brown/ Black wire (pin 2) connects to terminal 54 on the ECM. The Red/blue wire (pin 3) is the heater feed wire and connects to the front sensor heater wire and terminal 29 (fuse 26 in the fusebox). The Green wire (pin 4) connects to terminal 29 on the ECM.
For testing purposes you can use the following data:
With the plug disconnected the resistance between terminals 3 and 1 (the heater element) should be 6 Ω, with the plug connected and using a voltmeter between terminal 3 and earth, the reading should be 11-14V (battery voltage).
Testing the output from the engine control unit the reading from terminal 54 on the ECM with the ignition on but the engine not running should be 0.4V, with the engine running this should rise to 0.8V.
Hopefully carrying out these tests will expose the area of the problem which can then be rectified.