Alfa 159 JTDM DPF Regen & Differential Pressure Sensor

[whittye]

Hi All,

A work collegue had issue with a Volvo DPF and it cost him a packet. Snap, the following week the engine light came on on my Alfa 159 1.9 JTDM over a weekend while away from home. I plugged version 2.5 of this software into the car and found there was a "Differential Pressure Sensor Error" (P2452, P2453 or P2455 code - not sure which). Digging a bit more and found that there was a regen process happening sometime (could tell from the km's since last regen register) around when my engine light came on.

I cleared the fault and tried to run the DPF Regen manually and the error kicked in again when the car approached 3500 rpm. The car was running fine otherwise so I drove it back home and to a local mechanic, thinking a new differential pressure sensor would sort the issue. The partice filter was showing 49% blocked after the attempted manual regen.

The local mechanic phoned a friend (alfa dealer) who told him there was no point in doing anything that a new DPF was required at a cost of €1800 + VAT! The mechanic is going to order a new differential pressure sensor first to try that but has anyone else had a horror story like that?

The car has 96000 Kms on the clock. Strangely, the mechanic said, according to his scanner the DPF was 79% blocked - it was 49% blocked a few hundred miles previously.

Anyone else had a differential pressure sensor replaced? Did it cure your issue?

Indeed, anyone any idea how to confirm that sensor itself is faulty (as opposed to the ECU reporting a false failure as the mechanic suggests - logic: the ECU doesn't see what it expects to see hence it thinks it must be broken, reporting the fault)?

I just want to get out of this without buying a new DPF!

Hoping for help!

[s130]

Just be careful on the DPF % measurement figures.

I'm confused till I plug into my Croma and read the DPF % levels.

I'm fairly sure (but don't quote me on this unless other confirm) that 100% is 100% clear and likewise 80% is 80% clear and 20% clogged.

Typical Italian reverse logic going on.

If I'm right your 49% clogged is actually 51% clogged. After your forced regen the 79% would actually mean the clogging dropped from 51% to 21%.

A faulty pressure sensor could send the ECU a signal that ECU reads as "no regeneration required" and thus the filter will progressivley get more clogged.

Hopefully you pressure sensor error code is actually what has happened and that a new sensor will put everything back to normal.

Let us all know what happens.

[raf schils]

take your car on hiway, 3th gear at 4000 rpm for 10 min, take a breake (10 min)then 3th gear 3500 rpm for 10 min.if needet do it again, reset the foultcods. you see it realy works. some cars you have to reset once more 3 or 4 times . try it .greats Raf.

[whittye]

Thanks for the responses. The problem is when I take it above 3500rpm I get the "Differential Pressure Sensor Error" - driving or if running dpf regen manually. Anyone know how the Differential Pressure Sensor works electrically?

[s130]

Suggest you get the Bosch Part Number off your sensor and then goto ther Bosch technical website.

I did this for another Bosch sensor and could download the technical data sheet.

[whittye]

OK got a bosch sensor and repaced the original with it. Also replaced the sensor in the body of the DPF....no joy.

Should the Differential Pressure Sensor show a value while the engine is running normally (i.e. while not running a regen) in ECU Scan? Mine just shows 0.000 - even with the new sensor. The pipes look ok, blew them out with an air line too. Is there anyway to test the sensor itself?

The blockage level has increaced from 70% to 80% in 2 weeks so not sure what's going on, just fearful of it reaching a terminal state!

[whittye]

Quick update, after talking the mechanic out of changing the DPF for €1800, wasting money on a temp and differential pressure sensor I finally go to the botom of the issue - the hose going from the exhaust to the differential pressure sensor! I had asked the guy to check the hose (which of course he said he did) at the very begining of the ordeal. When I probed a bit further as to how he checked it before I shelled out on a DPF Unit, he had pressurised the open sensor end of the hose to check for blockage....never occurred to him there might be a leak! Anyways, when the hose was removed, sure enough, there it was, a pin hole!

Hose replaced now. Regen ran and blockage back down to 27%!