donfranco

hope somebody out there can help, i own a 525d sport 2005 plate its done around 83k, the car seems to go into limp mode when it pleases sometimes from start off and other times when i accelerate hard over 3000rpm, however when the car has warmed up it seems not to go into limp mode as much although you do need to re start the car. on a couple of occasions the waste gate can be heard very loudly. also the car is very sluggish and other times the turbo seems to over boost quite considerably

diagnostic message appears boost pressure control reading i cant figure out what this actually relates to, i have changed the injectors and i have had the engine valves replaced although this was another issue. the turbo has also been replaced over a year ago.

could the exhaust system and cat cause this problem. or is their a issue with my turbo although i can still hear the turbo whistling even in limp mode.

JasonH

If you had the injectors replaced they do need coding to the car. I think there are numbers stamped or engraved on each injector and these need to be programmed into the car using diagnostic equipment. If you don't do this you may get away with it because the car will adapt but you may not get the car running properly.

Anyway back to your problem. From what you are saying my guess would be that your turbo wastegate isn't operating properly. It could be physically stiff from carbon build up. In that case it it may stick open (no power) or not open when it should as the car changes up, in this case the car will go like stink but at somepoint the MAP (Manifold Air Pressure) sensor will detect too high a pressure and trigger limp mode.

It is possible you have a blocked DPF but to me it really sounds like the turbo wastegate control. This could be the vacuum supply to the actuator, the actuator, the adjustment of the actuator rod but I think the wastegate is simply sticking. See if you can move it by hand, I can just about move mine on my 535d, perhaps 5mm of movement, it's pretty stiff. I bet yours is solid.

Another possibility is a cracked exhaust manifold. If you get exhaust fumes under the bonnet the exhaust manifold is cracked and if a lot of air is getting in and exhaust leaking about the DDE (engine management) can get well confused and give erratic performance.

Regarding the lack of response, this forum tends to have more USA members than some others and that means more experise on petrol cars and less on diesels.

kammy6000

hello, my 525d 2005 just started going into limp mode last week
but it only does it when its at running temp or when i try to go fast

error codes:
3f97 = boost pressure too high
3ff0 = maf sensor
4521 = actuator too high
4166 = dpf pressure low

tried with maf removed bad idea became even worse no power at all so connected it back limp mode stays until engine is off for 5-15 minutes there are no errors on idrive no error lights! all i can hear is the turbo whining away but the car dont go if this is a boost leak where should i start please guys help me bring my car back

thanks

kammy6000

ok its my lambda sensor (o2 sensor pre-cat ) that's my problem to test you can disconnect if the car starts boosting like before then that's it ,it will still go limp mode because the sensor is disconnected after a bit

so now i need a diy guide which i cant find

does anyone have one please i need to do it straight away its suffering ,many thanks