DPF differential pressure sensor mbar readings

[H4wkeye]

Does anyone know what should the normal readings be? I did a quick test cuz I gotta clean the DPF it seems and at idle speed (750 rpm) it's about 4/5-7 mbar. Once I rev the engine to about 2000-2300 rpm, I've seen it jump to as high as 200mbar for a second. I didn't hold it at those revs, just a quick pedal push to rev it up.

[GiveMeABreak]

The sensor itself operates as follows:

The sensor consists of the following components:

• Electronics to amplify the signal
• A sealed membrane

The membrane is subject to the following pressures:

• The inlet pressure of the particle filter (upstream)
• The outlet pressure of the particle filter (downstream)

The sensor provides a voltage proportional to the differential pressure measured by the membrane (delta P = P upstream - P downstream)

Voltage supplied for a differential pressure of 0 bar: + 0,5 Volts (engine off).
Voltage supplied for a differential pressure of 0,9 bar: + 4,1 Volts (particle filter clogged).

"C": Sensor output voltage In volts.
"D": Pressure in Bars.

[H4wkeye]

So, how exactly does one read this? Do I need to know the voltage too? I was just reading live data off the Autel diagnostic.

[GiveMeABreak]

Well the voltage range on the sensor is only 0.5 Volts to 5V. You need to divide MBbar by 1000 to get Bar. So anything at 0.5 bar would show the filter 50% blocked for example.

[H4wkeye]

Ah, gotcha! Cheers Marc. Can the diagnostic show the voltage too, or do I need to measure it on the actual sensor itself?

[GiveMeABreak]

You can’t do anything about the sensor itself because the voltage changes as the diaphragm picks up the changes in the pressure from the DPF. If the sensor itself wasn’t working, then you probably wouldn’t be getting any readings.

I think you just need to accept that the DPF needs cleaning out Most likely.

[cit-rotti]

At idle, the differential pressure should be "0" mbar.
Whenever the throttle is opened properly, the differential pressure increases and then returns to the old idle value.
4-7 mbar at idle is not a particularly high value - the increase to 200 mbar when accelerating is quite high.
Carry out 1-2 forced regenerations - or cover a longer distance with a lot of power - or both.
If the value does not decrease, the FAP will probably have to be renewed or cleaned in the long term.

Greetings Wolfgang

[H4wkeye]

You can’t do anything about the sensor itself because the voltage changes as the diaphragm picks up the changes in the pressure from the DPF. If the sensor itself wasn’t working, then you probably wouldn’t be getting any readings.

I think you just need to accept that the DPF needs cleaning out Most likely.

Seems like that is the case indeed. I have no problem cleaning it, just wanted to make sure it was the cause of the problem most likely, so I don't go through the whole thing and spend the cash with no avail. Thanks for the assistance as always Marc! Also, after the cleaning procedure, I just need to tell the ECU that the filter was replaced correct? So it sets the proper values.

At idle, the differential pressure should be "0" mbar.
Whenever the throttle is opened properly, the differential pressure increases and then returns to the old idle value.
4-7 mbar at idle is not a particularly high value - the increase to 200 mbar when accelerating is quite high.
Carry out 1-2 forced regenerations - or cover a longer distance with a lot of power - or both.
If the value does not decrease, the FAP will probably have to be renewed or cleaned in the long term.

Greetings Wolfgang

Already tried several of that stuff. I also get "Regenerations too frequent" on the diagnostics. My guess is cause it's getting filled/full of cerine and stuff it keeps trying to regenerate itself too much but it's not working cuz it can't burn that off.

[GiveMeABreak]

Yes, once you've had it cleaned, just go into replacement parts and tell it that the DPF has been replaced. Whilst you are at it, top up the additive level and reset the additive counter as it's important to reset it in either case, as the ECU will be keeping count of how much additive has passed through the filter in grammes.

Correct the Cerine and other engine deposits and ash that can't be burned off will clog the filter walls over time.

[H4wkeye]

Yes, once you've had it cleaned, just go into replacement parts and tell it that the DPF has been replaced. Whilst you are at it, top up the additive level and reset the additive counter as it's important to reset it in either case, as the ECU will be keeping count of how much additive has passed through the filter in grammes.

Correct the Cerine and other engine deposits and ash that can't be burned off will clog the filter walls over time.

So the additive counter needs to be reset in any case? Didn't know that! Right now it's estimating it has about 900ml left. I will get a liter of additive too then. Which one should I get for my car?

If you need my VIN it's in this post viewtopic.php?p=716089#p716089

Also what happens if you reset the counter but don't top it up? Can you run out without the ECU actually knowing so you don't have any left to be injected?

[GiveMeABreak]

If this is for your 2010 X7, VIN ending 723, then your build date is 12147, so you need Eolys Extend.

[H4wkeye]

It's for that X7 indeed. I can't look at my VIN atm. And the forum is hiding it from me

[GiveMeABreak]

It's the one I have been using, so unless you've changed your car, this will be the one.

[H4wkeye]

Thanks Marc.

[H4wkeye]

And one more question how long does it take to take off the DPF and is it tricky to do?