Author Topic: Lambda sensor specification (Read 1692 times)

BrummPopBang · « **on:** January 13, 2020, 10:22:33 AM »

Does anyone know of the spec for the Lambda sensors on the Jazz 2005 petrol 1339cc L13A1?

I tested mine as per a YouTube demo. The tests where to measure as follows -

1) The resistance across the two white wires (heater)
2) On heating the tip of the sensor with a blow torch (MAPP gas which is apparently a mixture of propyne & propadiene), the DC voltage output from the grey and black wires.

Results-
Heater resistance: 15ohms
Sensor output: 7mV

A chap on YouTube measured 7.2ohms and 980mV.

Now 7.2 ohms at 12 volts is 20 watts. This is quite low in my opinion, but in conjunction with the hot exhaust gasses would probably help the heating process quite a lot to the tune of 200C-300C.

My 15 ohms is less than 10 watts of heat input, so I wonder if this is any use at all.

And although a Mapp gas flame may not represent the exhaust stream very well, I would expect a lot more than 7mV.

I'm awaiting delivery of an OBD2 scanner, so will report the output from that as and when...

Otherwise, any comments please?

Jocko · « **Reply #1 on:** January 13, 2020, 11:31:12 AM »

A heater is normally open circuit or alright. A cheap meter and leads can make a difference at low values too.

culzean · « **Reply #2 on:** January 13, 2020, 12:24:41 PM »

Quote from: Jocko on January 13, 2020, 11:31:12 AM

A heater is normally open circuit or alright. A cheap meter and leads can make a difference at low values too.

+1 either open or ok, on some meters the lead resistance is a problem on low resistance testing.

https://www.hella.com/techworld/uk/Technical/Sensors-and-actuators/Test-lambda-sensor-4379/#

sparky Paul · « **Reply #3 on:** January 13, 2020, 02:50:02 PM »

You can test that the heater is not open circuit with a multimeter, as Jocko says above, but it's not a reliable way to test the operation of the sensor, as the output fluctuates rapidly. There are also several different types of sensor, with different output characteristics.

OBD is the way to go, look for the repetitive fluctuating output from the pre-cat sensor on live data, once it's hot. Post-cat sensor should be much steadier, indicating that the cat is doing it's job. If you are getting that, the sensors are most likely working. You can also see the fuel trims being applied by the ECU from the sensor feedback.

The heater element is tiny, so doesn't need a great deal of power.

BrummPopBang · « **Reply #4 on:** January 15, 2020, 11:31:33 AM »

Thank you for all your replies. Most helpful.

Quote from: culzean on January 13, 2020, 12:24:41 PM

https://www.hella.com/techworld/uk/Technical/Sensors-and-actuators/Test-lambda-sensor-4379/#

That's a very helpful tech reference. Thanks.

Can anyone recommend an aftermarket replacement oxygen sensor please?

After doing a fair bit of investigation over the last few weeks, it appears to me that most sensors are going to be the same spec, and that seems to be-

Voltage output: 0.3-0.9V (mine is 7mV)
Heater resistance: Less than 10 ohms (mine 15 ohms)

I do have reasonable quality test meters, so anticipate realistic readings.

The problems I've had with the car for a few years now seem to fit the scenario of faulty sensors. I followed the same methods for testing as per several YouTube videos and whereas they all obtained similar results as per the above, mine are way out of the usual ranges.

I have an OBD2 meter on order, and take the point that a more realistic test is to see the values read by the ECU.