Limp mode on a C5 2.2HDi

[aramsay]

Can someone list all the "faults" that can contribute to a 2.2HDi going into "limp mode" ?

I have physically removed the Particle Filter element, and had it removed from the ECU, but I am still getting an error for "Engine Additive"....I assume this is the Eolys injection tank being empty.

Anything else that can be removed to stop the darn thing going limp ??

It's an '02 C5 Estate Exclusive, and apart from the above, is a superb car, hence why I wish to persevere with the limp-mode / Anit-Pollution fault........

[KevMayer]

If you have a Lexia there are some references to the particulate filter which need to be removed from the configuration of the BSI.

Limp Home Mode on a 2.2 Hdi can most often be caused by a turbo overboost which is due to leaks on the vacuum system which controls the turbo's variable geometry. With no vacuum the turbo defaults to max boost. So, if you've got a vacuum leak you'll have max boost all the time and so the ECU cuts the power.

[aramsay]

I did find some split vacuum pipes, and after fixing there, am fairly confident there are no leaks now. My swirl valve is operating OK. (with engine off.....top of rod is up-&-to-front of car / with engine idling....rod is down-to-rear)

Do you know, if the sensor on top of the intercooler is faulty....what does the ECU interpret this as...over-boost ?? Any idea how to test this sensor ?

[Chlorate]

Limp mode is just a knee-jerk reaction the ECU has to pretty much anything it sees going wrong with the engine management system - it does this in an attempt to prevent any additional damage happening to the car. Unfortunately the easiest way to find out what sensor/actuator/widget has gone wonky is to interrogate the ECU with a diagnostic tool (Lexia for Citroens).

If the sensor on the cooler is the MAP sensor, then if it's faulty the ECU would go into limp mode since it wouldn't know when to open the wastegate on the turbo. Unfortunately I don't know of a way you could test them apart from fitting one you know works and seeing if that clears the fault.

[Monkeyfeet]

If you've had the ecu mod'd properly then you shouldn't see any reference to additive at all. How was it done?
I didn't use Lexia at all to do this and had no error messages. ( I did use Lexia later, but only for curiosity really).
I don't think there is a wastegate on a diesel turbo , but the C5 turbo certainly is controlled by the vacuum pressure so getting rid of any leaks is definitely worthwhile.

[Chlorate]

I think you're confusing a wastegate with a dump valve there.
The wastegate is a valve often built into the turbo that opens to allow exhaust to by-pass the turbine thus restricting boost, which in this case is controlled by vacuum metered by the ECU.

[Monkeyfeet]

I think you're right, I'll certainly stand corrected on that one!