P0242 error code.

[stickery74]

I have a 2007 C5, 2.2Hdi. It runs fine most of the time, but every now and again will lose power, or even die completely and comes up with 'Depollution System Faulty' warning on the dash. Always restarts, but often in limp mode until it has been turned off for a while, and then runs fine again - until it doesn't. The fault seems to occur when i accelerate hard. A friend has an OBD2 reader which has thrown up P0242 code, which indicates Turbocharger/Supercharger Boost Sensor “B” Circuit High Input.
Any advice as to the best course of action to rectify this fault appreciated.

[wurlycorner]

Does your friends reader only show codes, or also freeze frame data set at the time of the code, or live data?
If it shows freeze frame data, what data PIDs and values has it stored associated with the code?
And if live data, leave it plugged in while you drive the vehicle, showing the boost values and next time the code sets, see what it's showing.

Without having the specific Citroen code-set criteria (perhaps someone will post that and it will give better direction); do you have any leaks on the exhaust system (either that you can hear or see)?

[stickery74]

Only codes - i googled the code to get the description. No obvious leaks, but i'm going to have a proper look at the weekend ( i'm working during daylight hours). Due to the Depollution fault message i'm hoping MAF / EGR or similar. I may be able to borrow a live data reader at the weekend so that might give more clues.

[wurlycorner]

Due to the Depollution fault message i'm hoping MAF / EGR or similar.

Depollution fault is just a generic message shown on the dash for basically any fault with the engine, I believe - don't take that to mean anything at all or get distracted by it and head off into guess work, imo.
The DTC and the data from that, is what to go on.

[stickery74]

Due to the Depollution fault message i'm hoping MAF / EGR or similar.

Depollution fault is just a generic message shown on the dash for basically any fault with the engine, I believe - don't take that to mean anything at all or get distracted by it and head off into guess work, imo.
The DTC and the data from that, is what to go on.

OK, good to know, Thanks.

[PaulC5]

I may be wrong but I believe the boost pressure sensor is the MAP sensor so you could check its wiring/connector. If you have a code reader that does live data you can see what pressure the sensor is giving. Definitely do not start replacing parts hoping to get the right one before wasting too much money. If you do not want to pay a Citroen dealer for a diagnostic then at least buy a code reader that shows live data which might help - they do not cost much but will not give a great deal of info when compared to dealer equipment, as an example https://www.gendan.co.uk/product_FXNT200.html

[stickery74]

I may be wrong but I believe the boost pressure sensor is the MAP sensor so you could check its wiring/connector. If you have a code reader that does live data you can see what pressure the sensor is giving. Definitely do not start replacing parts hoping to get the right one before wasting too much money. If you do not want to pay a Citroen dealer for a diagnostic then at least buy a code reader that shows live data which might help - they do not cost much but will not give a great deal of info when compared to dealer equipment, as an example https://www.gendan.co.uk/product_FXNT200.html

Thanks Paul, hoping to borrow a live data reader this weekend.