Technical Lambda question - which one is broken?

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Technical Lambda question - which one is broken?

richit

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I know there's already a lot about Lambda sensor on the forum but I can't find an answer to my issue.

The engine management light comes on after 30 mins or so and the OBD reads: "P0141 - 02 sensor heater circuit bank 1 sensor 2"

I went and bought a new Bosch probe only to be told my car has 3 of them. There are two on or around the exhaust manifold and one on the exhaust. From this fault reading can I say for sure which one is gone or do i just have to replace one after the other until the fault clears?

Many thanks!!
 
Hi, sorry can't help directly, my barchetta only has 1 lambada. However, can you try the new one you have bought in each location, try each time to see if the fault stops, to eliminate the bad one or are they different sizes of thread?
 
Thanks StevePD! That's what I was thinking. I'll wait a day or two in case someone knows something we don't and there's an easier way. I was amazed to find out it has 3!
 
I think I figured it out. I unplugged the two easier-to-get-at sensors on the engine, one at a time, and checked with the OBD tester. It came up with different faults so it had to be the after-Cat sensor. So, jacked up the car and unplugged it and the original fault came up - bank 1, sensor 2.

Looking at the engine you have one on the left (cylinders 1 + 2) and one on the right (cylinders 3 + 4), and the after-cat on the exhaust.

Left (cyl 1+2) P0135 - is Bank 1, Sensor 1
Right (cyl 3+4) P0155 - is Bank 2, Sensor 1
Exhaust P0141 - is Bank 1, Sensor 2

Somewhere else I read different codes so the best way to find out which of the three is gone is to unplug each one in turn and then check the errors.

I replaced it with a Bosch universal (all three sensors are the same). I decided to solder the wires together rather than use the supplied connection blocks and then shrouded them and then with special tape that bonds together. Whole thing took an hour, so very easy. Need to take it for a long drive to see if there's still an issue...
 
Well, if you have an OBD reader you could just unplug one of the lambdas and compare the error codes?
Also, I doubt that Fiat would name the only lambda in the previous version anything other than lambda 1, or change the numbering in the revised three lambda version, so I guess #2 is the mid or rear lambda?

And you can measure the lambdas from the connectors with a multimeter - the heater element is between the two white wires coming from the sensor, the black wire is the signal and grey is the ground. A working heater circuit will give you some resistance reading (measuring from the two whites), and a burnt one will not.
 
Yes, that's what I did. It was very easy. Hopefully all sorted now! I couldn't test with a multimeter as the fault was intermittent. I just had to find out what they were 'called'.
THANKS!!!
 
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Nice work! It's good to see some old fashioned ingenuity and logical thinking at work. Far too much car fault diagnosis these days simply involves plugging the wretched thing into a computer and then changing bits until the codes disappear.
 
Just an update on this: I found which of the 3 Lambda probes were at fault and replaced it. Now the car is fine. No more warning lights and it runs fine. Thanks for all the input!
 
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