DPF risk of particle filter becoming blocked

[pauljbl]

It got up to 400 deg if I was going uphill but soon dropped as went flat. Do you think the exhaust sensor could be at fault

[pauljbl]

Regeneration only becomes a problem if the exhaust gasses are not getting hot enough for either an assisted regeneration (450 °C) or passive regeneration (550 °C).

That won't be hot enough for a regeneration. In order to get an assisted regeneration, you'll need to get it to 450 °C, so will need to drive it in 4th gear at say 40 MPH for about 20-30 minutes, ideally with no stops / start traffic as a minimum to get the exhaust gasses to reach this temperature as a min.

Do you think the exhaust sensor could be at fault

[GiveMeABreak]

The exhaust temperature sensor is a resistive type sensor with negative temperature coefficient.

Once the temperature hits over 160 °C, the drop in resistance is very small the hotter the temperature is:

So I guess you should be able to see if the resistance corresponds to the temperature in the readings below (at least from a starting point of 10 °C upwards) until it reaches say 90°C, near operating temperature and see if the corresponding resistance in rows 4, 5, 6 & 7 change accordingly.

Minimum value (°C)	Temperature (°C)	Maximum value (°C)	Resistance R (In Kohms )
-50	-40	-30	133,8
-20	-10	0	46,76
-10	0	10	34,49
10	20	30	19,86
40	50	60	9,748
90	100	110	3,770
140	150	160	1,802
190	200	210	1,001
240	250	260	0,616
290	300	310	0,412
340	350	360	0,293
390	400	410	0,218
440	450	460	0,168
490	500	510	0,134
540	550	560	0,109
590	600	610	0,090
640	650	660	0,076
690	700	710	0,065
740	750	760	0,056
790	800	810	0,049
840	850	860	0,043

[pauljbl]

The exhaust temperature sensor is a resistive type sensor with negative temperature coefficient.

Thankyou. I noticed when at idle just sitting there it seems to stay around 100 deg

[pauljbl]

The exhaust temperature sensor is a resistive type sensor with negative temperature coefficient.

With the active regen does the engine not try to get it hotter with extra fuel I was reading or not on this car?

Do you get a message on the dash when regen is happening?

[GiveMeABreak]

Hi

No message on the dash during regeneration.
Post injection is used but not as much as on some other manufacturers engines.


Ascertaining the required level of regeneration assistance

There are two types of regeneration assistance, depending on the thermal status of the exhaust line:

• Level 1 regeneration assistance (cartographic maps for cold exhaust pipe and catalytic converter) (catalytic converter pre-heating, up to 250°C)
• Level 2 regeneration assistance (mapping for hot exhaust line. Temperature higher than 250°C)

Level 1 regeneration assistance
When the monitoring function estimates that the soot level is considerable and that the capability of the engine to regenerate the particle filter (driving conditions, temperature, etc.) is sufficient, it requests the activation of the level 1 regeneration assistance.

When each activation request is issued, the engine management ECU carries out the following operations:

• Prohibition of regulation of EGR (exhaust gas recycling)
• Request for activation of electrical consumers (Heated rear screen ; Heated mirrors ; electric cooling fan unit)
• Under-setting the main injection to increase the exhaust temperature
• Manipulation of the air mixer

Level 2 regeneration assistance
The principle is identical to the level 1 regeneration assistance, but the addition of post-injections allows the temperature of the exhaust gas to be higher.

The change from level 1 to level 2 regeneration assistance depends on the following conditions:

• Exhaust temperature
• Until the temperature has reached 250°C

The engine management ECU activates one or two post-injections depending on the engine speed and the engine load.

[pauljbl]

Hi

No message on the dash during regeneration.
Post injection is used but not as much as on some other manufacturers engines.

Just trying to understand here it says it can regenerate once got to 250 deg but you said it needs to be 450deg

[GiveMeABreak]

No, that's not the same thing - this is the temp at which it decides to use one or the other regeneration strategies, not the actual regen. temps.

[pauljbl]

No, that's not the same thing - this is the temp at which it decides to use one or the other regeneration strategies, not the actual regen. temps.

Oh OK so if your driving and its about 250deg the ecu trys to get the temperature up to 450deg for a regen is that correct?

[GiveMeABreak]

The engine ECU will use multiple strategies for attempting regeneration based on the driving conditions and the driving history as to the best way forward. If all these fail for example lots of short journeys, or interruption (engine switched off during or just before a regen), then it will attempt a regen at the earliest opportunity - failing this it will ultimately flag up the warning 'Risk of Particle Filter Clogging' at which point you are advised to go for a decent run to get the vehicle to temperature for regeneration. If this is unsuccessful, the vehicle will ultimately go into reduced power mode to prevent damage tot he engine if the exhaust is blocked. If the particle filter gets anywhere at approx. 70% or over, there's an increased possibility that assisted regeneration won't be ale to complete and the filter will have to come off for cleaning.

[shtu]

OK, few things to catch up on for me...

The diagbox pump test does produce about 20ml from a healthy tank and pump. A fwd drops like you got points to a problem. A spare pump isn't a lot cheaper than a brand-new complete tank assembly, and less hassle.

Your filter pressure readngs are high, higher than mine pre-clean which would trigger the P1490 fault code. About half those values seems nearer correct.

If you still have the old dpf, I'd go for a proper try at flushing that out, see the other thread. It took me HOURS of washing to get it to the point that nothing was coming out of the filter, but it's worked.

There are figures in the diagnostics about how recently a regen has happened, which might be useful to you.

[pauljbl]

OK, few things to catch up on for me...

The diagbox pump test does produce about 20ml from a healthy tank and pump. A fwd drops like you got points to a problem. A spare pump isn't a lot cheaper than a brand-new complete tank assembly, and less hassle.

Your filter pressure readngs are high, higher than mine pre-clean which would trigger the P1490 fault code. About half those values seems nearer correct.

If you still have the old dpf, I'd go for a proper try at flushing that out, see the other thread. It took me HOURS of washing to get it to the point that nothing was coming out of the filter, but it's worked.

There are figures in the diagnostics about how recently a regen has happened, which might be useful to you.

I gave the old dpf a good clean off the car and the pressures are much lower now about 3mbar idle and 80mbar at max revs.

I did get a brand new tank and ran the flow test but still not getting 20ml I got more than the old one but about 7ml. Am I doing the test correct. I connected a pipe from the tank pump to a measuring device and ran the test in diabox don't understand why not 20ml from a new one

What version of diagbox do you use?

[pauljbl]

The engine ECU will use multiple strategies for attempting regeneration based on the driving conditions and the driving history as to the best way forward. If all these fail for example lots of short journeys, or interruption (engine switched off during or just before a regen), then it will attempt a regen at the earliest opportunity - failing this it will ultimately flag up the warning 'Risk of Particle Filter Clogging' at which point you are advised to go for a decent run to get the vehicle to temperature for regeneration. If this is unsuccessful, the vehicle will ultimately go into reduced power mode to prevent damage tot he engine if the exhaust is blocked. If the particle filter gets anywhere at approx. 70% or over, there's an increased possibility that assisted regeneration won't be ale to complete and the filter will have to come off for cleaning.

Is there a best version of diagbox you would reccomend for this 2012 Citroen.

Also on a new additive tank I couldn't get it to change from 1litre capacity to the 2litres I had filled it with. If I go into the fuel pump in diagbox and read the values it says 2 litres. But then if I go into the engine ecu it says 1litre. I did the press the fill tank option in both the fuel pump section and the engine ecu section but stays at 1 litre

[Paul-R]

Is there a best version of diagbox you would reccomend for this 2012 Citroen.

I use 7.58 on our 2013 X7 with no problems. It's stable with few bugs. 7.57 would probably work just as well, I only updated to get better access to our 2015 308.

[GiveMeABreak]

Also on a new additive tank I couldn't get it to change from 1litre capacity to the 2litres I had filled it with. If I go into the fuel pump in diagbox and read the values it says 2 litres. But then if I go into the engine ecu it says 1litre. I did the press the fill tank option in both the fuel pump section and the engine ecu section but stays at 1 litre

As I mentioned previously the values are calculated, not physically measured. The issue may be because it has not been correctly reset - you should be setting the additive counter to zero.

Make sure to use the priming function and also note that you may need to do this is 2 areas if it is not resetting - sometimes in the engine ECU, by selecting and confirming the ECU after a global test, then in the engine ECU menu there should be some options for operations concerning the additive / DPF system, but you'll have to have a hunt around. The other area may be in the main repair menu in Diagbox, again have a look for similar functions until you find the right options. I can't be more specific as these often change with different software versions and models.