C4GP 2009 1.6HDI TED Engine.

[pauljordanie]

Thank you both for the help - i'd be lost without it! I checked the MAF with a scope and I can see the frequency increase and decrease with a change in air flow. I also checked the turbo actuator and the actuator pops up quickly without any drag/hesitancy. I've checked the pipes from the vacumm side and the turbo side and they are good and hold a vacuum. The third pipe, in the red circle on the pic, where is that, and is that a filter on the end of the pipe, I assume this is the atmospheric side? The turbo solenoid on the back of the engine doesn't have the cap on the end with the integrated air filter. Could I pull that third pipe of the actuator and see how it goes for a mile or two.

[GiveMeABreak]

That is not the correct circuit for your car! Similar but not the same. According to your VIN it should be this one:

1 is the Vacuum solenoid valve and pipe 8 is the Vacuum Union.

[MikeT]

I've seen several variations of turbo solenoid that appear to have been revised around the filter. Older ones had a user-serviceable round sponge filter, externally-housed in either a rectangular or round pull-off part, while later versions had the same round sponge filter fitted inside the top cap of the solenoid itself (which is crimp-sealed to the main body and not meant to be user-serviceable) whereas the one that came off my X7 has a fine mesh screen filter over a round plastic frame and is fitted inside the main body.

[pauljordanie]

The turbo spools up ok, but then I get the over boost problem. Looking at live data when driving when I floor the accelerator I can see the boost hit approx 2400 and then the MIL light comes on - I scan and read P0238. I think this is pointing to a problem in loosing the vacuum when boost isn't required. Where does pipe 8 go/connect to, is it just an open port to dump the vacuum?

[MikeT]

Pipe 8 is the atmospheric feed, it is completely seperate to the vacuum (in/out) ports and allows the solenoid plunger to travel freely regardless of the pressure the other side of it's diagphram.

[pauljordanie]

I've tested all the pipes connected to the solenoid and they all hold vacuum (with one end blocked of course). I removed the solenoid and connected to 12V and no clicking noise. The Vac port on the solenoid holds vacuum but also pulls vacuum on the pipe to the turbo. Would I be right in thinking that I should hear the clicking of the solenoid once I energise?

[GiveMeABreak]

Here's that P0238 code for info for this engine:

Fault code	P0238
After sales description of the fault code	Turbocharger pressure signal: Short circuit to positive
Description of the diagnostics	Short circuit to positive or open circuit Value too high (Above 4.8 V)For 1,2 second
Conditions of activation of the diagnostics	Consult the associated contexts for the Pcode forwarding conditions
Conditions of disappearance of the fault	Ignition on
Down-grade modes if fault present	Default value for the air flow as a function of the engine speed and of the flow injected Inhibiting of the diagnostics and air flow sensor plausibility Cutting of the EGR butterfly (turbo air cooler), EGR valve and bypass butterfly (inlet air heater) in all operating modes
Switching on of the warning lamp and/or warning message	Warning lamp MIL
Main customer complaints likely	Noise Diesel fuel consumption a bit higher Lack of power
Suspect areas	Turbocharging pressure sensor Turbocharger position copy sensor Vacuum problem Variable geometry of the turbocharger jammed in the "maximum turbocharging" position Faulty turbocharger