which temp sensor is inside the dpf

[lapka]

I have a Mazda5 and there's an issue with the DPF. During the regeneration temperature rises too high and the P2428 error pops up. This is on the sensor B1S2. Which one - out of the three sensors - is this? I was sure it was the middle one, but replacing it didn't change anything. Today I checked the other set of values in Forscan (EXHTEMP1, EXHTEMP2, EXHTEMP3) and it would appear that EXHTEMP2 corresponds to B2S1 and EXHTEMP3 to B1S2). So, after all, which sensor is the middle one, located in the DPF itself - B1S2 or B2S1 - and which one is the last one (after cat)?

[FORScan]

B1S2 - Bank 1 sensor 2
B1S1 - Bank 1 sensor 1
B2S1 - Bank 2 sensor 1

EXHTEMP1 - B1S1, upper
EXHTEMP2, B1S2, middle
EXHTEMP3, B1S3 , lower

Bank - cylinder line (side). 4 cyl engine usually have only 1 bank. V6 and V8 engines usually have 2 banks. It is easy to determine number of banks looking at exhaust pipe.

Sensors are numbered from the engine (upper) to the output (lower).

[lapka]

Thanks, but the readings say that EXHTEMP2 is equal to B2S1 (CATT21_DSD).

Moreover, after a lot of searching on the web I found this:
https://euroesi.mazda.co.jp/esicont/eu_ ... 02500.html

It says that:

CATT11_DSD
Indicate the catalyst temperature.
(Before exhaust gas passes through catalyst converter.)
—
CATT12_DSD
Indicate the catalyst temperature.
(After exhaust gas passes through diesel particulate filter.)
—
CATT21_DSD
Indicate the catalyst temperature.
(Before exhaust gas passes through diesel particulate filter.)

which would mean that B2S1 is the midle one (after catalyst converter, before DPF).

Anyway, I'll check it today by simply unplugging the sensors and checking the readings.

[FORScan]

Both B1S1 (CATEMP11) and B2S1 (CATEMP21) are before the cat (as also mentioned in the document you referred to).

Here is the screenshot that illustrates sensor numbering:

Sensors_locations.jpg (161.43 KiB) Viewed 21538 times

If your engine is not V6 or V8, it should have no B2S1 at all.

[lapka]

Actually, it's not about the O2 sensors, but exhaust gas temperature sensors which are named in the same convention.

And yes, I can confirm now that (at least for RF7J engine in Mazda5):
B1S1 = CATT11_DSD = EXHTEMP1 = before the cat
B2S1 = CATT21_DSD = EXHTEMP2 = after the cat, before the DPF
B1S2 = CATT12_DSD = EXHTEMP3 = after the DPF

which can be a little misleading, because the order in which they appear in all monitoring tools is B1S1, B1S2, B2S1.

Replacing B1S2 solved my issue with too high temperature.

[pkomi]

lapka, I seem to have very similar problems with my DPF in my Mazda6. Temperature sensor B1S2 shows very high temperatures during regen as seen in these two graphs. Is this more or less what you experienced as well? FORScan was the first OBD software to allow me to see the error codes nicely. Where did you manage to source the replacement sensor?

Situation during DPF regeneration. Sensor B1S2 rising rapidly

obd.png (28.68 KiB) Viewed 20995 times

B1S2 over 800C and P2428 appears

obd2.png (27.33 KiB) Viewed 20995 times

[pkomi]

I have now also replaced my B1S2 exhaust temperature sensor and the previous problem seems to be gone. Monitoring the temperatures during auto regeneration do not show ridiculous values anymore.

[carlus]

lapka, I seem to have very similar problems with my DPF in my Mazda6. Temperature sensor B1S2 shows very high temperatures during regen as seen in these two graphs. Is this more or less what you experienced as well? FORScan was the first OBD software to allow me to see the error codes nicely. Where did you manage to source the replacement sensor?

obd.png

obd2.png

Hi pkomi. Please could you tell me what program you use to get the graphs that you put it?

Thanks

[pkomi]

Hi pkomi. Please could you tell me what program you use to get the graphs that you put it?
Thanks

These graphs are made with OBD Auto Doctor, but FORScan offers similar graphs too.