Xantia – Oxygen sensor and AL4 gear

lancia58 · Post by **lancia58** » 01 Dec 2010, 06:51

Hi

I connected the Lexia 3 to my car and entered to the engine diagnosis and selected display parameters. All of the parameters looks OK but the Oxygen sensor reading. It idle it varies between 120mv to 800mv , the engine ECU is not reporting any fault but I guess the reading of the Oxygen sensor should be stable at idle , BTW just for the test I drove the car while the Lexia is connected and the Oxygen sensor readings was unstable as well. Does this indicates on a faulty Oxygen sensor or should I check that the Oxygen sensor connector conduction is OK.

Than I tested the AL4 again with the Lexia connected while I was driving. In the parameters screen I looked in the current gear. At stop it reads 1 as it should, when the AL4 changed to the second gear it read 2 as it should but when it changes to the third gear it reads 2 while it was expected to read 3 and when the Al4 changed to the fourth gear it read 3 . Is this is the normal behavior of the gear field in the parameters screen of the AL4 ? Is there a reason why AL4's gear 3 and 2 displayed 2 ?

Thanks
Zohar

addo · Post by **addo** » 01 Dec 2010, 07:13

Your oxygen sensor does produce a voltage that changes, typically in about four steps.

A healthy sensor begins around 250mV, then steps up over just a few seconds, to eventually finish around 950-1000mV.

With the AL4, the best way to determine what gear it is actually in, is to look at the tachometer. In first gear, the tachometer needle greatly exceeds the speedometer in degrees of rotation. Second gear has the tachometer more advanced by 30-40° clockwise.

In third, the needles are moving almost perfectly parallel, while in fourth the tachometer needle is retarded 25-30° behind the speedometer position.

lancia58 · Post by **lancia58** » 01 Dec 2010, 07:57

But is it logical that in idle without pressing the gas pedal the Oxygen sensor readin will vary between 150 mv to 800mv ?

addo · Post by **addo** » 01 Dec 2010, 08:19

It is totally normal. This is referred to as "cycling". A healthy sensor cycles in steps of approximately equal millivolts; for example 250-450-650-850.

Generally, oxygen sensors in a well-cared for motor will last longer than the replacement part manufacturers suggest - my sensor is still quite good at 160.000km and I don't see any need to change it.