Does this look right? Pressure diff DPF and P2454/P2002

[Daneontheroad]

Hi all

I get the Engine Malfunction indication on the screen but usually not the MIL and these errors (Using Forscan Lite for Android)

Code: P2454 - Particulate Filter Pressure Sensor 'A' Circuit Low
Code: P2002 - Particulate Filter Efficiency Below Threshold (Bank 1)

The DPF, hoses and pressure diff sensor have all been renewed and I still get the errors. The reading during operation can look like in the first image, and I don't know if that looks right. The fluctuations look odd and are also very high and seem unconnected to engine load. The revs did not change much and there was no change in engine sound.

At other times the readings are much lower and seem more sensible as seen in the next image. There you can also see that when I get the error message the reading drops to zero.

I suspect a ground issue or problems in the wiring harness but that is mainly because I have run out of things to replace. Any help would be greatly appreciated. Thanks.

Car: S-Max 2006 2.0 TDCi 140 HP

[Tizer]

No, the readings should be quite steady when your right foot is steady.

The Screenshots would make more sense if you monitored the Accelerator Pedal Position, RPM and Speed as well as the Differential Pressure and if the Time Scale was shown as well.

If the old Differential Pressure Sensor gave similar results and it was not an aftermarket one that someone had replaced in the past then you are probably correct about a Wiring fault or a faulty PCM.

In the second Screenshot it looks like you may have floored the Accelerator Pedal in the middle and the Differential Pressure went to 0 when you did that. If so then that is the opposite of what I would expect.

Edit, I would also monitor the MAP as well as the other things to see if Boost Pressure is also doing strange things.

[Daneontheroad]

16 hours ago, Tizer said:

No, the readings should be quite steady when your right foot is steady.

The Screenshots would make more sense if you monitored the Accelerator Pedal Position, RPM and Speed as well as the Differential Pressure and if the Time Scale was shown as well.

If the old Differential Pressure Sensor gave similar results and it was not an aftermarket one that someone had replaced in the past then you are probably correct about a Wiring fault or a faulty PCM.

In the second Screenshot it looks like you may have floored the Accelerator Pedal in the middle and the Differential Pressure went to 0 when you did that. If so then that is the opposite of what I would expect.

Edit, I would also monitor the MAP as well as the other things to see if Boost Pressure is also doing strange things.

Cheers, I'll try to monitor those as well. And you are right, I did accelerate when the DP_DPF went to 0, and that is strange. Happens every time.

[TomsFocus]

2 hours ago, Daneontheroad said:

Cheers, I'll try to monitor those as well. And you are right, I did accelerate when the DP_DPF went to 0, and that is strange. Happens every time.

Is it possible the pipes are fitted the wrong way round?  So the pressure appears to go down when you accelerate instead of up?

[Daneontheroad]

37 minutes ago, TomsFocus said:

Is it possible the pipes are fitted the wrong way round?  So the pressure appears to go down when you accelerate instead of up?

I guess. But how to check? I don't even know where the sensor is located and if access is from above or below?

[TomsFocus]

2 minutes ago, Daneontheroad said:

I guess. But how to check? I don't even know where the sensor is located and if access is from above or below?

Just swap the pipes over and check the live data again.

Should be accessible from above but I'm not totally sure where it'll be on your car.  They're usually on the battery box or on the bulkhead.  If you can't see it initially, follow the pressure pipes up from the DPF itself.

[unofix]

Just like on Blue Peter, here's an S-Max post I answered earlier 🤣

 

[Daneontheroad]

13 minutes ago, unofix said:

Just like on Blue Peter, here's an S-Max post I answered earlier 🤣

 

 

Thank you for that. I am thrilled that you directed me to the SSG-site since I didn't know anywhere to locate exploded drawings 👍😃

[Daneontheroad]

35 minutes ago, TomsFocus said:

Just swap the pipes over and check the live data again.

Should be accessible from above but I'm not totally sure where it'll be on your car.  They're usually on the battery box or on the bulkhead.  If you can't see it initially, follow the pressure pipes up from the DPF itself.

Thank you. Unofix just showed me the SSG website where this lovely image is available. Apparently you are right about the location but judging from the length of the wires only mechanics with gorilla arms can reach it from above 😄

[Daneontheroad]

On 8/28/2023 at 4:30 PM, Tizer said:

No, the readings should be quite steady when your right foot is steady.

The Screenshots would make more sense if you monitored the Accelerator Pedal Position, RPM and Speed as well as the Differential Pressure and if the Time Scale was shown as well.

If the old Differential Pressure Sensor gave similar results and it was not an aftermarket one that someone had replaced in the past then you are probably correct about a Wiring fault or a faulty PCM.

In the second Screenshot it looks like you may have floored the Accelerator Pedal in the middle and the Differential Pressure went to 0 when you did that. If so then that is the opposite of what I would expect.

Edit, I would also monitor the MAP as well as the other things to see if Boost Pressure is also doing strange things.

Here is a new screenshot where I cruise along with DP_DPF looking fine. Then I floor it and the Engine malfunction lights up as seen in the second image (without turning on the MIL). This automatically reduces the engine load even with the pedal on the metal, and the DP_DPF disappears and the MAP drops. Revs and speed even grow (I was going slightly downhill). The graph shows 30 seconds.

Does this enlighten us more?

Fingers crossed.

[Tizer]

9 hours ago, Daneontheroad said:

Does this enlighten us more?

Very strange, I can't make my mind up whether you have an electrical or mechanical problem, or both.

If you bring the MAF PID up as well and recreate the problem then the MAP and MAF graphing should be the same as each other. If they are not then I would be looking for a mechanical problem.

It is strange that the RPM and speed did not go up much when you briefly had Max Boost. You can change the scale in FORScan to micro analyse things later, so changing the RPM scale from 0 to 10000, to 0 to 5000 or less may show some more detail.

[TomsFocus]

That's just limp mode.  Torque is reduced but you still have power.  There's less boost, so less exhaust flow, which means less pressure difference between the top & bottom of the DPF core.

What fault code was triggered when the malfunction message came up?

[Tizer]

5 minutes ago, TomsFocus said:

That's just limp mode.  Torque is reduced but you still have power.  There's less boost, so less exhaust flow, which means less pressure difference between the top & bottom of the DPF core.

It does seem to be Limp Mode Tom  but the strange thing is that the Boost before and after Limp Mode is the same, unless the EGR or Throttle Valve are doing something strange, which is unlikely, so there can't be less Exhaust Pressure after Limp Mode but it is showing zero Differential Pressure after.

@Daneontheroad, did the car work ok at some time and then developed a fault or is the car new to you and the fault has always been there.

[Daneontheroad]

10 minutes ago, Tizer said:

@Daneontheroad, did the car work ok at some time and then developed a fault or is the car new to you and the fault has always been there.

First I want to say how great it is to have you guys doing what you can to help. Thank you for that!

I have had the car for several years and on a camping trip to Germany this summer it broke down going up a steep hill in hot weather. The duct from the intercooler cracked with an audible puff and started to wheeze, power went down, the car generated lots of smoke and the MIL lit up. We limped 150 km to the campsite after that.

A local garage changed the duct but the exhaust was blocked and leaked through the flexible section by the cat. Repairs were too expensive there so we drove 900 km home like this, sometime smoking A LOT. At home we got a new cat, new DPF, enw sensor and new hoses for it. And here we are.

My non-informed guess is that the original DPF clogged up bc of faulty wiring to the sensor or maybe bc of bad hoses to the sensor and that this error persists. But I am in no way an expert.

Did that make sense?

[Daneontheroad]

43 minutes ago, TomsFocus said:

What fault code was triggered when the malfunction message came up?

I don't know exactly what the code was but they are always either P2454, P2002 or both. Sometimes accompanied by others but those two are regulars

[TomsFocus]

9 minutes ago, Daneontheroad said:

I don't know exactly what the code was but they are always either P2454, P2002 or both. Sometimes accompanied by others but those two are regulars

Hmm.  Those aren't very helpful codes unfortunately.  P2454 could be either wiring or sensor.  P2002 is virtually useless as that just shows that the pressure differential is out of spec - we can already see that on the graph.

The fact that the DP reading returns again after a restart suggests that it's not a physical fault with the DPF or the pressure pipes.  Even if the pipes were fitted the wrong way round, I'd expect an immediate return of 'some' pressure after letting off the throttle.

It looks like a bad sensor to me, membrane getting 'blown out' by a hard thrash and then gets stuck in position for a while.  Also 'waves' about under normal load instead of producing the steady readings we'd expect.

But I wouldn't want to totally rule out wiring at this stage.

[Daneontheroad]

8 minutes ago, TomsFocus said:

Hmm.  Those aren't very helpful codes unfortunately.  P2454 could be either wiring or sensor.  P2002 is virtually useless as that just shows that the pressure differential is out of spec - we can already see that on the graph.

The fact that the DP reading returns again after a restart suggests that it's not a physical fault with the DPF or the pressure pipes.  Even if the pipes were fitted the wrong way round, I'd expect an immediate return of 'some' pressure after letting off the throttle.

It looks like a bad sensor to me, membrane getting 'blown out' by a hard thrash and then gets stuck in position for a while.  Also 'waves' about under normal load instead of producing the steady readings we'd expect.

But I wouldn't want to totally rule out wiring at this stage.

I'll poke my head under the hood this evening and see what I can see. Maybe test the sensor. I even have a spare if I can access the thing.

[Tizer]

That is interesting background information @Daneontheroad, maybe there is a restriction in the Exhaust downstream of the DPF like a flap of metal that restricts the flow under heavy load, limp Mode kicks in and at the next restart the restriction is not there until under full load again. 

This might seem unlikely but a similar thing happened to me years ago but it was a flap of plastic in the Air Filter, that was before cars were Electronically controlled.

I agree with Tom that the DPF Sensor or Wiring is the most likely cause.

[Daneontheroad]

All is well after I swopped the hoses around from the DPF to the sensor. The mechanic had connected them the wrong way

i runs very well now and I am happy.

Thank you again for your help and interest!

 

[Tizer]

I'm glad it was an easy fix and well done to Tom for guessing correctly early on.

On the bright side, armed with what you have learned here and FORScan, if something else goes wrong with the car you may be able to diagnose what is wrong without taking it to a Garage. 

[Daneontheroad]

7 hours ago, Tizer said:

I'm glad it was an easy fix and well done to Tom for guessing correctly early on.

On the bright side, armed with what you have learned here and FORScan, if something else goes wrong with the car you may be able to diagnose what is wrong without taking it to a Garage. 

Yes to both 🙂

BTW the sensor can be seen from above after removal of the air filter assembly and the battery and battery shelf but I wasn't sure I could work on switching the hoses around in the available space and ended up doing it from below on the DPF itself. FYI