Quick Lamda question...

[noelboy]

I've got a 3 wire lamda sensor that I'm trying to get a reading from.
To my way of thinking the shell of the lamda and the cable that runs to it would be negative, then the second wire would be positve and the 3rd wire would be signal.
For some reason if I meter it at that I get a negative reading.
The only way I can get a positive reading is to run positive to the shell of the lamda (the bit that bolts to the exhaust)....is this right?

Thanks

[RobbieV]

Isn't one of the wires a heater wire ? (Don't worry iam clueless [img]/wink.gif[/img] )

More info if it helps :

<a href="http://www.picotech.com/auto/lambda_sensor.html" target="_blank">http://www.picotech.com/auto/lambda_sensor.html</a>

[Stupink]

iirc white with black stripe is signal.. or is it black. lol.. i never can remember what colours they are.
lambdasensor.co.uk or .com have the wiring diagrams for lots of them, shows heater/signal wires etc.

[T.F.S.]

THREE WIRE SENSOR
(sorry caps)

middle wire is siginal 0.4-0.8v output at idle (this is to check that it works at all it is not to test condition)

the other two wires are ign live and a neg to the heater, these are normally white in color but *IIRC* are purple in the loom, the siginal is normally black but it is always the odd color out

[the_one]

iirc,
1 wire- black = signal,
2 wire-black = signal, grey = ground for signal,
3 wire- black = signal, grey = ground for signal, white = heater (+)(earthed through body of sensor),
4 wire- black = signal, grey = ground for signal, white = heater (+), white = heater (-)

hope that helps

[the_one]

P.S
the signal should swing from about 0V to about 1V every second with a warm engine