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crwdns2944351:0crwdnd2944351:02010 Mazda 5 How to Troubleshoot Oxygen Sensorcrwdnd2944351:0crwdne2944351:0

crwdns2933797:0LarsWHcrwdnd2933797:0crwdne2933797:0

crwdns2936043:0crwdne2936043:0 crwdns2933505:0crwdne2933505:0 LarsWH

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Oxygen sensor
Type
technique
Title
How to trouble shoot oxygen sensor
Introduction
One year after replacing the rear oxygen sensor of my 2010 Mazda 5, the yellow engine warning symbol came on again. I read out the error code, with my 'OBD 2' device, and it was again reporting fault code P0138 ("bank 1 sensor 2") problem [link|https://cartreatments.com/p0138|https://cartreatments.com/p0138/][br]
As the device was fairly new, I susptected it was something else. Clearing the fault code while the engine was warm, seemed to work, so I suspected the built-in heat element was not working. However the fuse #37 was OK (see [link|https://www.autogenius.info/mazda-5-2007-fuse-box-diagram|https://www.autogenius.info/mazda-5-2007-fuse-box-diagram])
I then removed the sensor and cleaned it using ultrasound (and gazonline), but that did not solve the problem.
In disbelief I went on and checkes all (!) the relays, but they alle seemed OK
Finally I decided to order a new sensor from a webshop (somehow all webshops I found seem to share the same Berlin address...). This is the part I ordered: [link|https://www.motordoctor.dk/products/8126770-lambdasonde|https://www.motordoctor.dk/products/8126770-lambdasonde]
Before mounting the new sensor, I did a non-scientific check of the pins, which I enumerated like this:
# Top left
# Bottom left
# Top right
# Bottom right
And then I checked it with a multi-tester like this: [link|https://www.aliexpress.com/item/1005001566461938.html|https://www.aliexpress.com/item/1005001566461938.html|new_window=true]
{table
|width=50%
|format=30%l:r:c
|! Pins
|! New sensor
|! Old defect sensor
|--
| 1-2
| 5.06 Ohm
| 6.2 Ohm
|--
| 1-3
| 48 pF
| 6.5 Ohm
|--
| 1-4
| 49 pF
| 52 kOhm
|--
| 2-3
| 46 pF
| 0.9 Ohm
|--
| 2-4
| 49 pF
| 53 kOhm
|--
| 3-4
| 46 pF
| 53 kOhm
}
As you can see from the table above, there clearly is a difference in the behaviour of the new and the old device.
I installed the new device and followed the instructions:
* clear the error codes
* disconnect the car battery for som minutes
* take the car for a 10 minute drive
After this, the problem was gone.
Time Required Min
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Time Required Max
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Difficulty
Moderate
Conclusion
Leasson learned: probe the oxygen sensor pins if you experience problems:
* Pin 1-2 is the pre-heating element, and should show around 5-6 Ohm (meaning that the pre-heating must be using around 60W)
* All other combinations of pins should show a capacitance around 50 pF
Here are some good resources on Mazda and oxygen sensors, but remember: meassure the pins and look for signs of a defect device before you start taking tings apart
[link|https://www.youtube.com/watch?v=jFFR4307AIQ|https://www.youtube.com/watch?v=jFFR4307AIQ]
[link|https://www.youtube.com/watch?v=XC5HWd7Pin4|https://www.youtube.com/watch?v=XC5HWd7Pin4|new_window=true]
[link|https://www.youtube.com/watch?v=fiOxH14JPEE|https://www.youtube.com/watch?v=fiOxH14JPEE]
[link|https://www.700r4transmissionhq.com/p0138-mazda-3|https://www.700r4transmissionhq.com/p0138-mazda-3]
Author
LarsWH
Public
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