huet564

Could someone please advise me of Lambda sensor voltage(approximate) output at tickover

My sensor gives 0.05 volt(with respect to earth) when cold.
0.6 approx. when hot
i don't think it's any good.
Thanx. Stu

pat

Stu,

the lambda sensor output should not be steady at idle, it should rock between about 0v and about 0.7V but it can go a bit higher on occasions. This is basically the ECU trying to maintain the AFR at 14.7 for the 3 way cat to work properly. You cannot "trust" the output voltage since it is temperature dependant, all that you can "trust" is the sharp change in output from 0 (lean) to greater than 0.7 (rich) around the stoichiometric point.

By rocking the mixture around this "step" in output voltage, the ECU can be reasonably confident that it is maintaining an average of 14.7....

What you have descibed sounds sort of right.... when cold you get no output (or very little). When hot it will react, but it "feels" like your sensor isn't fully hot yet and is reading 0.6 instead of 0.8 (the car runs rich while warming up). It should then go to the "rocking" behaviour descibed above.

Hope this helps,

Pat.

huet564

Thanx for the advice Pat, i think i get it.

could you give any advice on testing the sensor as i'm getting really poor MPG. on the motorway and i've been advised it could be lambda sensor.

Thanx again Stu

scoobyboy

what model yr is it coz if it's an 01my they do have a separate afr sensor to the o2 sensor

pat

scoobyboy,

I find highly unlikely that it would be an MY01, that would've been a very short lifespan for the lambda sensor, PLUS the front AFR meter would maintain fuelling correctly for cruise hence wouldn't cause poor MPG figures.... I will therefore assume it is an older car

Stu,

One way of testing the O2 sensor is to take it off the car and heat it up with a blowtorch (think that's hot? it can get to over 1000 degrees C in the headers!). With a voltmeter connected to the ouptut and the case, it should read about 0V when it's not in the flame, and over 0.7V when it is in the flame (as there will be little or no oxygen there). Another simple test is to keep it on the car and get some heat into it, then keep thje car on high boost so it will be running pretty rich, it should read at least 0.8V if it doesn't then it may be duff. But remember when it gets really hot, the output falls again.

Hope this helps,

Pat.

huet564

Thanx again Pat,
Did a similar test today, left sensor in downpipe, with a wire coming from the output to a meter. took the car for a thrash, when on full boost, the Lambda output was o.8v, come off throttle, output = 0v, normal driving, output = 0.4 - 0.7v. Sensor maybe o.k after all.
Thanx again Stu (97 U.K Scoob)

scoobyboy

pat it's electronics i've allready changed 2 of the afr sensors on my01s they can go wrong at any time.

Sam Elassar

hi pat

so what does 0.8v correlate to in co% terms ?

Sam Elassar

hi pat

so what does 0.8v correlate to in co% terms ?