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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 | | 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. |
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