Turbo not working no boost

**obews** · 27-08-2008,06:59 PM

Hello all this is my first post.
I own a VW 02 T4 CARAVELLE TDi 102 bhp ACV engine.
So far I have replaced all the vacuum pipes,checked the wastegate actuator -ok - and renewed the N75 Boost control valve.
Bought Ross Tech Vag com recently and found 4 faults -

17964 Charge pressure control neg. deviation P1556-35-10 -- intermittent
17849
17564
17569 Manifold temp. sensor (G72) open or short to plus P1161-35-10 intermittent

Can anyone explain these faults or advise anything else to try - missing my turbo!
THANKS OLWYN

**Moose man** · 30-08-2008,10:34 PM

Hello.

Possible MAP sensor.

**obews** · 31-08-2008,08:45 AM

Hello and thanks for the reply,

I'm no mechanic but am willing to try anything to get the turbo back !
Havn't heard of a MAP sensor before so could you enlighten me please .
Thanks Olwyn.

**Moose man** · 31-08-2008,05:36 PM

Hello.
After making a note of the codes did you clear the fault code memory and drive the vehicle again?? Some of the codes could be old ones and they might send you up the garden path with the diagnosis. Try that first and see what 'fresh' codes are stored. It's best not to just start replacing parts, that usually works out very expensive!!!!!!

**obews** · 31-08-2008,08:38 PM

Thanks again for replying, I just tried to clear the faults but it won't let me .
Going to give Ross Tech a buzz to find out how to clear them and I'll get back in touch.
Olwyn.

**obews** · 01-09-2008,05:49 PM

Have managed to clear the old codes today and took it a spin - plugged it back in and just 1 fault now -

17964 CHARGE PRESSURE NEG. DEVIATION P1556-35-00

Any ideas on where and what to try next please !

**Moose man** · 01-09-2008,09:17 PM

Does your diagnostic equipment allow you to do actuater tests? If it does you can check the operation of the boost actuater system. While carrying out the test, with the vehicle stationery!!!, you can be visually inspecting the turbo waste gate rod to make sure its moving. Check and double check all the hoses to make sure you haven't missed one with a split, it only takes one small leak to drop the vacuum enough to cause a problem. It's a fail safe system so if there is not enough vacuum to operate the system properly the waste gate will stay in the no boost position, safe mode.
Come back with your findings.

**obews** · 01-09-2008,09:59 PM

Hello,
I have checked the actuator with the missus revving the engine - no movement! but you can move the arm by hand.
I have been told that the wastegate opens with pressure and there's none at the pipe.
I'll check the pipes again and see if the software can do an actuator test. Thanks Olwyn.

**Moose man** · 02-09-2008,10:45 PM

Hello.
There should be a vacuum at the pipe that leads to the waste gate/variable vain actuator. As soon as the engine is started the arm should move as the vacuum is applied. To control the boost pressure the vacuum is switched on and off very quickly by the boost pressure solonoid which in turn is controlled by the ECU. If the arm isn't moving at all when the engine is started it means the variable vain is in the no boost condition. You won't be able to generate enough load on the engine by revving it stationery to require the ECU to control turbo boost, so you wouldn't get the waste gate to work even if the system was working correctly. You need to find out why there is no vacuum at the pipe.
Don't give up!!!!

**obews** · 03-09-2008,07:21 AM

Dear Moose man can't thank you enough for the interest !
As you can tell I don't know what I'm doing but will try. I will try to get a vacuum gauge today and try to see if the wastegate actuator moves on startup !
I now know why fault 17569 manifold temp. sensor was there before - started the van while the intercooler was out and that I assume would have logged the fault.
Speak again later thanks Olwyn.