Hi


That's it really, how do I test the lambda sensors to see if they are working? my car is using a lot of fuel and one cause could be dead sensors.


I have connected the signal wire of one of them to a multimeter and get a steady reading of 4.7V when it should cycle between 0 and 5V.


Does anyone know whether 5V = rich or lean?


There are no codes coming up in the OBD reader.


Cheers


Glen

 

Can your OBDII reader display a live datastream? Mine does and I can see the voltage swinging. Not perfectly, because of a mismatch between the cycling frequency of the O2 sensor and the data refresh rate of the scan tool.

It can never hurt to replace them, it's NTK #25018. I can find them in Canada for about 1/10th the price Jaguar wants for an identical thing. The factory parts say NTK on them!

 

As above, the best way to test is with Live Data which you should be able to see even with cheap interface and phone based software. Be aware that most interfaces/software assume Zirconia sensors and seem to limit peak volts at about 1.5v - you will still see the swing which is the important part - I have only found Jaguar IDS interface/software to not have that constraint.

The sensors are Titania sensors and as you say should swing in the range 0-5V. The sensors work by receiving a Reference voltage from the ECU (~5v) and pull that signal to ground with a variable resistance (to ground) through the sensor as the oxygen content varies.

Lean = High Resistance (to ground) = High Volts on signal/ref wire

Rich = Low Resitance (to Ground ) = Low Volts on signal/ref wire.

Would be worth checking you have a good ground signal to the sensors if you have a pegged high voltage.

While testing normally, you can induce a lean condition by pulling a vac hose and induce a rich condition by spraying some Easystart in to the air intake. These tests would normally peg the voltage reading high/low.

 

Hi


How do I check for a good ground signal? continuity between earth and the earth wire on the sensor?


I have done the air leak and 456 (cyls) sensor didn't change in value - pegged at fully weak already, the 123 sensor increased in value as expected.


My car runs on LPG, so I used butane to do the second test (rich). The car didn't like it one bit, I had to keep the revs high to prevent it from stalling.


456 sensor still didn't change
123 sensor seemed to increase slightly instead of falling which threw me a bit.


I will check the ground on both and if good, replace 456. SNG do one for a good price.


SNG Barratt - The Ultimate Jaguar Parts Specialist


Glen.

 

How do I check for a good ground signal? continuity between earth and the earth wire on the sensor?

I'd check for resistance rather than continuity. Continuity can give a false reading even with a fairly high resistance.

My car runs on LPG

As a general principle I'd switch to petrol if you can for doing testing to eliminate any issues with the LPG system, and then repeat tests on LPG if appropriate.

 

OK, how many Ohms am I looking for?


Cheers


Glen

 

I'd expect to see 1 or 2 ohms but I'd be happy with anything single digit.

 

OK, I was just about to fit new Lambdas when someone on the LPG forum said that the yellow ref (in) wire should be providing 5v to the lambdas.


When I checked my wiring I get this on both of them


Black (Ref out) = 4.7v
Yellow (Ref in)= 12v engine off, cycles between 7v and 14v at idle
Red = (Heater +) =12v
White = (Heater -) = 0v


So too many volts going in = to many coming out via the black wire?


Can anyone confirm what the voltages should be?


Cheers


Glen

 

The wire colours I see on the diagram are upstream of the connector to the O2 sensor, so you might have to look there.

I see a blue/pink and white/green to the heater circuit. That gets ignition switched power on white/green and grounds through the ECU on blue/pink. For cylinders 1,2,3 the sensor circuit has a blue and blue/purple wire., for cylinders 4,5,6 it's red and blue/purple.

The blue show 0.1-4.7V swinging at idle. Blue/Purple shows common ground signal between both sensors.

Looking at my XJR and comparing the wiring diagrams, the black wire on the O2 sensor is the signal, yellow is the power to the lambda circuit.

If you open up the harness a bit, you will see one of the wires is shielded, and thus fatter than the rest. This is the variable voltage signal wire to the ECU.

 

Many, many thanks


The 456 sensor is confirmed dead, so I have fitted a new one and both are now swinging as they should. the car runs so much better too.


Glen.