DPF pressure sensor problems

[Thorfinn]

Hi, seems a regular topic.

This could be coincidence but I have just had the Altitude Pressure Sensor replaced due to fault codes. A few hundred miles later get the P2453 DPF Diff pressure sensor fault and the P0472 Exhaust Pressure Sensor (are these two sensors combined?).  The curious thing is that this was coupled with the fans running at full tilt (as when the DPF is doing a regen and the engine revs at tickover increase) constantly, even though engine not up to temp. After about 30 miles the light went out but the fans kept on running at full speed.

This morning I got the faults cleared and initially the fans were still running high but after a 10 mile drive these stopped and returned to normal revs.  No warning lights on. Drove a further 8 miles and still OK.

Is this familiar to anyone.  What's going on?  Car is booked in for Wednesday but if faults are intermittent?

Thanks for any help.

[silver1011]

By far the most common DPF related sensor to fail is the exhaust gas pressure sensor.

 

Stick G450 into the search bar for plenty of bedtime reading!

[Brimma]

By far the most common DPF related sensor to fail is the exhaust gas pressure sensor.

Stick G450 into the search bar for plenty of bedtime reading!

Does the car perform noticeably better when this is changed?

[mannyo]

All the sensor does is measure the exhaust flow before and after the DPF, it has two pipes running into it from the exhaust. If the difference between the two reaches a certain point then a regen is performed.

 

If the sensor fails completely the car will have no idea if the DPF needs a regen or not, so over time the DPF will continue to just clog up as the car will not perform an active regen.

 

As soon as the G450 fault is recorded the sensor should be replaced and the required sensor adaption carried out. Just because the fault code clears does not mean that the car is getting meaningful info from the sensor. For example it could be telling the ECU that the DPF if fine whilst its clogging up, or could be telling the ECU to perform a regen when in fact the DPF is clear.

 

If the sensor is working and no G450 fault code then replacing will make no difference to performance.

[Thorfinn]

Thanks for that Mannyo, very informative.  Just to be clear, given that the two fault codes for Exhaust Pressure Sensor and DPF Diff Pressure Sensor were recorded, is this a single G450 sensor that measures both parameters.  Could this fault cause the fans to run at high speed or is that something else?  

 

Cheers. 

[silver1011]

The fans are running at speed as the car is either performing a regen or thinks it is performing a regen.

 

If a sensor is playing up then I'd imagine the chances of the fans running would be quite likely (although I never saw this when my G450 sensor failed. I simply got the EML).

 

The idea of the fans running is to cool down the DPF and exhaust system if the regen is interrupted (i.e. you turn the engine off midway through a regen).

Edited 29 July, 2014 by silver1011

[mannyo]

Thanks for that Mannyo, very informative.  Just to be clear, given that the two fault codes for Exhaust Pressure Sensor and DPF Diff Pressure Sensor were recorded, is this a single G450 sensor that measures both parameters.  Could this fault cause the fans to run at high speed or is that something else?  

 

Cheers. 

 

Both faults, same sensor.

[Thorfinn]

Many thanks for the replies. The car is in tomorrow but doubt they will have a sensor in stock. I will get it done as soon as for piece of mind.