2.2 hdi Blocked diesel filter message ECU faulty???

[printertosh]

Hi all
My peugeot 807 2.2hdi 2004 has gone into limp mode. I can get round it by unplugging the pressure differential sensor underneath the car which only leaves the yellow engine light and anti pollution fault on display but at least turns off the limp mode. I thought this pointed towards the pressure differential sensor in the exhaust being faulty (when I removed the pipes it did have some water inside) and was thinking of replacing it but now I'm not sure. I've read a lot online that this sensor should have a 5v feed to 1st pin (I have 4.98v), an earth to the 2nd pin and the 3rd pin should be a return to the engine ECU with information from the sensor (so I'm guessing this should show 0v when connector is unplugged), however my 3rd pin is showing 4.91v which appears to be coming from the engine ECU. Does anyone know if this means the engine ECU has short circuited inside and putting out a voltage rather than letting one in???
I'd be very interested to hear if anyone else has had a blown ECU from water getting in the pressure differential sensor.
Thanks to everyone in advance.
Paul

[fucco]

Hi,
I had nearly the same fault.....I always refilled the additive by myself and did not care about service intervalls.....suddenly I got the message "exhaust system defect...Abgassystem defekt in german)
I went to my garage and they computer told us: broken filter (teilweise durchlöcherter partkelfilter) the wanted to change the filter/diff-sensor and refil additiv (cost estimation: 1200 euro)
I told them that I don´t believe the nessage and asked for the actual pressure display....there was 0mbar - so the only possible reason for this behavior was the diff-sensor....I cleaned the sensor with pressed air (there was some water inside)....and after resetting the failure list everything worked

But: the reason for the failure was not the water, it was the bordcomputer!...this stupid thing doesn´t read the sensor information after an failure....(sorry for my poor englisch).....once the sensor send a bad or wrong signal the computer decides to ignore "good" siganls and you have to reset everything

But if somebody knows how to "trick" the signal by a dummy sensor, I would like to know the solution....on a working sensor the differential pressure is from: 10mbar to 80mbar...above 80mbar the regeneration will be activated

Regards

[Luc_C5]

Hi,

@printertosh

I seen in documentation about Differential Pressure Sensor that correct pins are:

1 Pressure information (0,5 to 5 volts)
2 Earth
3 5 volts supply

Voltage supplied for a differential pressure of 0 bar : (± 0,5 volt) (engine off) .
Voltage supplied for a differential pressure of 0,9 bar : (± 4,1 volts) (particle filter clogged).


@fucco

Dummy sensor can be made in the same way I designed the FAP temperature sensor.
I just need some time to study the values he send to ECU computer: pressure - voltage.

[printertosh]

Thanks for your replies.
Had another look at the voltages today. With the engine off I've had a an improvement to 1.7v and now only getting a bleep everytime I pull away to say the filter is blocked but the yellow engine light has now gone out and NO limp mode! I'm convinced that this suggests that the Pressure differential sensor is faulty. I might have to replace it and see what happens. I'm sure that the ecu relies on the pressure differential sensor being connected and acting as a variable resistor to be able to bring the voltage down to 0.5v. If you disconnect the sensor and test the end of the wire coming from the ecu you get a constant 4.91v from the number 1 pin - pressure information (not 0v as some have suggested), Earth from 2 and constant 5v feed from 3. I'm guessing with the engine off and the pressure equal either side of the sensor the electrical resistance of the sensor is at it's greatest. Once the engine is running and the pressure either side is not even the electrical resistance of the sensor reduces, if the pressure difference gets too great the sensor eventually allows too much voltage through (more than 4.1v) and declares the particulate filter blocked.

Please let me know your thoughts on this and hopefully this information could prove useful to others. Thanks again. Paul

[Luc_C5]

I checked my spare differential pressure sensor in my laboratory:

I supplied +5v to pin 3 and -5V ( GND ) to pin 2.
on pin 1 the voltage it is ~0.5V

if I blow in one of the pipe connection voltage increase till ~ +1V
if I blow in another pipe then voltage decrease until 0 and from there to ~ -V.

so the documentation it is correct.

Regarding your checking on pin 1 from ECU without sensor connected it is correct;
I think on the pin 1 from ECU it is a voltage divisor this is why without sensor connected you have +4.9v, and this value according to documentation correspond to a clogged filter and it is correct.

[printertosh]

Thanks very much for the information Luc C5. I took the sensor off the car today and connected +5v to pin 3 and -v to pin 2. Voltage tester showed 1.7v from pin 1 so that confirms that the sensor was damaged by the water in the pipes. I've ordered the new parts for £65.00 including VAT for Sensor, Bracket, Pipes and 4 Clips. Peugeot say that it has been modified, I presume to stop the water problem. I read somewhere that the sensor is placed at a different angle on the newer Peugeots to prevent this. I will post some photos on here if it is different to the original so people can see the modification. Thanks again. Paul

[londonirish]

printertsoh:
I just saw on the French www.planete-citroen.com forum that some guys had the same problem because of a sensor which had been exposed to water. As a result it was displaying "Antipollution Filter Error" whereas it was only the sensor...

[printertosh]

Problem fixed. Completely new design for pressure differential sensor. (jpegs attached). No need to reset light on dash at Garage/Dealer. Took the fuel cap off for 20 seconds, put it back on and took it for a drive. Then took it off again, put it back on and eventually when you start the yellow engine light isn't lit.
Thanks for everyones input. Hopefully this can help people with similar problems. Obviously a design problem so probably worth replacing the old design sensor if you have any problems with FAP. If you have the old design pressure differential sensor and +5v is going into pin 3 -0v on pin 2 and you have anything other than 0.5v on pin 1 when ignition is on but engine not running then water has probably got inside and broke it. Paul