[winjohn]

I have a Golf Plus 2.0l Tdi which started going into limp mode occasionally about a year ago but would reset if switched off. The problem slowly got worse until into permanently displayed the engine light so I took it in to be fixed.
The garage diagnosed the fault as

16618 PO234 000
Charge Air Pressure Sensor G31
Control limit exceeded
Sporadic

According to the manual the first thing to do is to check all earths on the wiring and clean. They did this, the light no longer came on, cost £80. They suggested I try the car and if it wasn't fixed then the next step is to change the wiring loom...cost £400!

The car still has the fault. It is OK if a stick below 3000rpm but on the motorway if I go above 80mph it will usually go into limp mode again although sometimes it won't.

I can't see how this is a wiring loom fault.

The other thing I have noticed is that the torbo whistles a lot under acceleration...could this be an air leak?

Any suggestions?

The garage say they will do another diagnostic but it will cost another £40, surely if they have not fixed the fault then it should be free?

John

 

[chittychittybangbang]

It could be an airleak, no way to know if you have one unless you do a boost leak check: http://www.myturbodiesel.com/1000q_how_to/multi/limpmodetdi.htm Sometimes it's the EGR pipes - they crack or the bolts are loose and it leaks out there. It could even be a bad MAF air sensor.

An overboost is normally cracked vacuum lines, N75 solenoid, wire to N75 solenoid, bad VNT actuator, or sticking VNT vanes. These are just guesses since your case may be different. http://www.myturbodiesel.com/1000q_how_to/multi/limpmodetdi.htm See this article and go step by step to narrow it down.

 

[Mrryan]

After they cleaned the grounds the light went out but the problem is still there? Sounds like a sticking turbo vanes or not reponding vanes. The turbo is always whistling during acceleration.

 

[winjohn]

After they cleaned the grounds the light went out but the problem is still there? Sounds like a sticking turbo vanes or not reponding vanes. The turbo is always whistling during acceleration.

Yes, but if the vanes were sticking wouldn't it always go into limp mode everytime rather than intermittently?
As for the whistling, it is a lot louder than it used to be.

John

 

[Fluid]

It could be sticking a little at first resulting in delayed response. Then it gets worse as there's more sticking.

 

[winjohn]

Thanks.
I have a problem that the garage just want to go through the manual which says the next step is a wiring loom change! I feel they should be investigating other options first, but I guess they are keen to charge me a nice four hours of labour for replacing a loom.
John

 

[chittychittybangbang]

Have them put it in writing that if changing the wiring loom doesn't solve it for 30 days you get a full refund plus interest. Or put the money in escrow. Their work hasn't solved it yet so why would you put your trust in them further.