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Old 16th June 2013, 22:45
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MadDogMoggy MadDogMoggy is offline
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Location: Dorset
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Had another play with the O2 sensor wiring today.

Rewired the heater using a switched 12v to power a relay, which in turn feeds the O2 sensor's heater. Turned off the error reporting on the ecu (since the heater circuit no longer connects to it) and checked the heater was getting a supply - all working fine.

I managed to find the part number for the correct primary O2 sensor for the type R. Turns out I have 2. I removed the one I currently have fitted using a 4 way connector I bought from CBS and replaced it with a spare I had which still has the original connector on. I found the female part and wired that into the loom.

Warmed the car up and checked the voltage of the O2 sensor. At idle it fluctuates from about 0.16v to 0.20v. Revving or blipping the throttle causes it to drop as low as 0v and then it recovers back to about 0.2v.

This is the 3rd sensor that I have used which gives this low range, instead of an expected 0.2v to 0.8v.

The car's booked in to a local garage on Saturday to get the emissions checked. With the heater now working they may be all right, but I still think the ECU is measuring a low voltage. If this is the case, the only thing I can think or is that there must be a large amount of resistance in the sensor circuit somewhere which is reducing the detected voltage: perhaps I have a poor connection in a plug or a wire not fitted right.

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