Recap of main points that don't seem to have already been disproved...
Titania have two heater wires (Red positive and White negative), they then have a signal reference (Yellow wire) which is fed with a 5V reference signal and an output which is on the Black wire and is the reference minus the internal resistance. The output can be measured with a meter with respect to ground but with the difference in potential between battery ground, body ground and ECU ground being only a few millivolts and the range being 0-5V, any difference will be negligible.
Mmm, well I have double checked and I am getting:
Black = 4.7v
Yellow = 12v engine off, cycles between 7 and 14v at idle
Red = 12v
White = 0v
I shall see what the X300 forum have to say too.
Possible problem with the 5v reference on the yellow wires then? But could yellow wire reference reach 7v/12v if there were no electrical load at all, such as maybe in case of broken probes? Would think ref voltage would stay the same anyway? And in any case even if ref voltage could reach higher voltage with disconnected or broken probes, the probes are still outputting 4.7v (not same as yellow wire voltage), so probably implies probe is at least putting some load on yellow wires. But this assumes probe uses same earth wire as the heater circuit to pull yellow wire ref voltage down to output signal voltage. Or what else could be going on? If yellow wires should be 5v (so if ref voltage is incorrect) could they be disconnected from the petrol ECU and another 5v regulator used to hold yellows at 5v?
I'd have a probe about with the meter once you've disconnected the sensor if I was seeing that.
Me too Bri. Might run the meter past the old and new probes too, see if there is much difference between old and new probes in terms of readings between all of the pinouts (2 pins at a time of course, a few combinations there...). If that doesn't reveal anything it might not be best idea to just plug in new probes at this point? Thinking that could damage new probes if something really is amiss with yellow voltage.
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