DPF health check

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

User avatar
GiveMeABreak
Forum Admin Team
Posts: 21577
Joined: 15 Sep 2015, 19:38
x 2163

Re: DPF health check

Post by GiveMeABreak »

Soot gets burnt off during regeneration.... then fills up again until the next generation is triggered - that's what the differential pressure sensors are for.

User avatar
osx
Donor 2020
Posts: 620
Joined: 08 Jun 2013, 20:09
x 5

Re: DPF health check

Post by osx »

So the DPF is absolutely fine as it is able to regenerate completely (not sure if a few grams of soot is something to worry about)?

User avatar
GiveMeABreak
Forum Admin Team
Posts: 21577
Joined: 15 Sep 2015, 19:38
x 2163

Re: DPF health check

Post by GiveMeABreak »

No, not the soot. But as the filter gets gradually blocked with the other non-combustible items I mentioned previously, then over time the pressure differential will increase as it becomes clogged and regeneration will no longer take place. So you'll get a warning when the filter is at risk of clogging and a message on the LCD display when it starts to have problems.

User avatar
osx
Donor 2020
Posts: 620
Joined: 08 Jun 2013, 20:09
x 5

Re: DPF health check

Post by osx »

What would be a normal pressure differential?

User avatar
GiveMeABreak
Forum Admin Team
Posts: 21577
Joined: 15 Sep 2015, 19:38
x 2163

Re: DPF health check

Post by GiveMeABreak »

The Diff. Press. Sensor consists of electronics to amplify the signal and a membrane.

So the voltage from measured from 0 to 4.5V, determines if the filter is blocked or not:

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).

User avatar
osx
Donor 2020
Posts: 620
Joined: 08 Jun 2013, 20:09
x 5

Re: DPF health check

Post by osx »

Isn't this the reading from the differential pressure sensor? Seems to be very low (3 mbar).

https://www.frenchcarforum.co.uk/forum/ ... &mode=view

User avatar
GiveMeABreak
Forum Admin Team
Posts: 21577
Joined: 15 Sep 2015, 19:38
x 2163

Re: DPF health check

Post by GiveMeABreak »

Yes that's the current reading. You want the reading to be low....

1000 millibar = 1 bar and the sensor operates from 0 bar to 0.9 bar (0 to 900 millibar). So a reading of 3 millibars shown in your screenshot is near to zero on a scale of 0 to 900 means the filter is perfectly normal and not clogged as you would expect after a regeneration has taken place. This reading will fluctuate and be different each time you run the diagnostics - because of the different state of clogging of the filter at the time you take the reading and whether a regeneration has taken place or not.

User avatar
osx
Donor 2020
Posts: 620
Joined: 08 Jun 2013, 20:09
x 5

Re: DPF health check

Post by osx »

Not sure why a sensor would report pressures outside the operational range but if accurate it looks like the DPF is in pretty good condition even after all these miles!

The car has been behaving for the last couple of week but am noticing some ?hesitation especially under low throttle. Reminds me of the EGR issues I had with a previous C5 - would it throw the same code if the EGR was playing up?
As for P0215:
Fault Code: P0215 - Supply relay control - short circuit to earth or short circuit to positive or open circuit
Description Main Relay Stuck
Conditions for Fault to clear: The following conditions have to be met:
- Engine idling (For several seconds)
- Engine cut following a phase in which the engine management ECU becomes dormant
Downgrade Modes whilst Fault is active: None
Symptoms: Starting Problem
Suspect Areas:Engine fuse box, Electrical harness, Connector
So this is likely to point to the fuel supply relay - which is contained in the engine fuse box. The relays are not really user serviceable, so the whole fusebox is generally replaced. You might find that it behaves for a while, but may start getting progressively worse - other symptoms can include cutting out / hesitation whilst driving.

User avatar
GiveMeABreak
Forum Admin Team
Posts: 21577
Joined: 15 Sep 2015, 19:38
x 2163

Re: DPF health check

Post by GiveMeABreak »

osx wrote:
27 Jul 2020, 14:47
Not sure why a sensor would report pressures outside the operational range but if accurate it looks like the DPF is in pretty good condition even after all these miles!
It's not outside the operational range though..It's showing 3 millibars which is inside the 0 to 900 millibar range.
osx wrote:
27 Jul 2020, 14:47
The car has been behaving for the last couple of week but am noticing some ?hesitation especially under low throttle. Reminds me of the EGR issues I had with a previous C5 - would it throw the same code if the EGR was playing up?
Not really, that fault code is specific to that issue. If the EGR was jammed or stuck it would show another fault code. It also has a self-cleaning / anti sticking routine. And by self-cleaning / anti sticking, I only mean it has a strategy to operate the valve a few times every time the engine is switched off to help prevent it sticking and not that it stops the unit from clogging up at some point. But if after self-testing it is not returning to the specified position then one of a few codes can appear.

User avatar
osx
Donor 2020
Posts: 620
Joined: 08 Jun 2013, 20:09
x 5

Re: DPF health check

Post by osx »

Fuse box replaced. Didn't need any programming. Low throttle response is better.

User avatar
GiveMeABreak
Forum Admin Team
Posts: 21577
Joined: 15 Sep 2015, 19:38
x 2163

Re: DPF health check

Post by GiveMeABreak »

That's correct, main engine fuse boxes don't need programming.

So has that cured your P0215 supply relay problem fault code now?

User avatar
osx
Donor 2020
Posts: 620
Joined: 08 Jun 2013, 20:09
x 5

Re: DPF health check

Post by osx »

The fault code didn't reappear after I deleted it (even after driving the car with the original fusebox for a month).
Haven't ran a diagnostic with the replacement fusebox but when I tried a used 2017 one I got all sorts of errors and engine didn't even start. Will probably see the errors from that attempt!