[Alpha242]

My 2012 V6 keeps going into limp mode If you accelerate harshly but no eml on! it is however storing code P0235 boost pressure sensor failure, I quite clearly have a leaking intercooler lots of oil and tested with a smoke machine confirms this. My mechanic thinks that is the issue, however my worry is I have read a lot of posts about leaking Intercoolers but none mention that theirs has gone into limp mode, although expensive I’d rather the intercooler than the turbo ? any ideas? Oh and I forgot to mention if you turn the engine off and back on it is back to normal again until you reach 2-3k RPM then back into limp.

 

[landmannnn]

I would be surprised if the leaking intercooler would throw up a code.

 

[Alpha242]

Exactly but could it cause the running problems listed?

 

[Alpha242]

Sorry I misread your post! But could the code be a product of the boost being lost due to the intercooler? And could the intercooler cause the running problems?

 

[landmannnn]

Normally the intercooler just has a minor leak, I suppose that if the leak has opened up it will upset the boost sensor.

 

[omar_zn]

My intercooler was leaking and I didn't know until I did the upgrade to a 50% larger cooler.
However, there a was a fault with the exhaust gas pressure sensor which triggered the engine light and limp mode.

Once I changed the sensor it was all good.

Seems to be common problem from what my mechanic told me.

 

[Alpha242]

So update..
intercooler replaced all pipes and vacuums checked, boost pressure sensor changed, boost solenoid changed, still no difference!
Going by live data it seems I have a serious overboost issue with boost reaching 50psi at points! Any idea what could be causing such serious overboost?

 

[freemansteve]

Possible stuck turbo vanes?

 

[Alpha242]

That’s my fear! Do you know is there any possible way to free them up without removing the turbo? As I reeeaaaaally don’t want to do that.

 

[freemansteve]

I don't know, but someone on here may recommend a product, or a procedure to free it.
I suspect the problem is not the vanes, but you seem to have eliminated a few other components already. Is there a way to check the BCS is actually working?

 

[Alpha242]

I don’t know to be honest perhaps someone does know how to test it? My last sensor I’m going to try before i condemn it is exhaust pressure sensor, I have read a lot about them failing and I’m not too happy with the reading I’m getting from live data which is 0.54v and doesn’t really fluctuate. I would be expecting it around 5v.

 

[landmannnn]

Agreed that the boost control solenoid might not be getting vacuum. That sounds more likely than a turbo issue

 

[Alpha242]

Do you know how I would test that? Where does it get its vacuum from? And could that cause such overboost?

 

[landmannnn]

Not sure, probably not thinking about it.

The manual says the condition of the code:
• ECM detects open circuit of turbocharger boost sensor
circuit for 0.4 second or more.
• ECM detects short circuit to power supply of turbocharger
boost sensor circuit for 0.4 second or more.
• ECM detects short circuit to ground of turbocharger
boost sensor circuit for 0.4 second or more.
• Difference of turbocharger boost sensor value and
barometric pressure sensor value is 160 hPa or less for
2 seconds or more when ignition switch ON.
• Difference of turbocharger boost sensor value and
barometric pressure sensor value is 200 hPa or less for
10 seconds or more while running the engine at idle
speed.

And possible cause
Harness or connectors
(Turbocharger boost sensor
circuit is open or shorted.)
• Turbocharger boost sensor
• Barometric pressure sensor
(built into the ECM)

 

[Alpha242]

Still no luck really, every sensor I replace seems to improve it a little but the limp still returns!

I am getting a few consistent codes these are;
P0235 turbo boost sensor
P0470 exhaust gas pressure sensor
P1525 ASCD function

Occasionally I get P2263 TC system.

And today for the first time I got P2002 DPF, this was after I tried some higher grade fuel, not sure if it related or not though.

A few guys on the Aussie forum think it may be a poor earth, has anyone over here experienced earth issues?

Or can anyone more technical than me spot a link between the DTC’S above?

 

[mrw27]

Vehicles can do some crazy things when subjected to poor conductivity at earthing point etc.

And your DTC's seem wildly far apart, which bad earths so very often cause.

It's something to check. You need to find out where they all are, and there's a few. Clean them up and reassemble. Some are more likely to cause trouble than others.

What is the mileage in this Nav?

 

[Alpha242]

Hi and thank you, it’s done 84k, looks fairly tidy under the bonnet and I have seen no corrosion yet on any of the connectors I’ve pulled apart, however that may be leading me into a false sense of security! If only I find a furred up earth is the source of the problem I will be very happy. Def worth a look though like you say.

 

[mrw27]

It's maybe not easy to get to some of the earths, but it's cheap.

Also, with regard to dissimilar metals and electricity (unlike a box connectors for example) is that some strange physics take place between the two metals when you pass a voltage through them.

I won't go into it but basically, earths (where two different metal conductors touch) spontaneously break down and eventually become open circuit. Galvanic corrosion.

 

[Alpha242]

So to prevent galvanic corrosion your best bet is to try and ensure both metal surfaces are as sound as possible?

 

[mrw27]

You can prepare and clean the electrical joint with something like THIS.

I would avoid using anything else since it could act as an even better electrolyte than the atmosphere itself and accelerate the whole process.

You might find a decent electrical contact assembling compound of some description, graphite based maybe, but a good thorough clean and reassemble would do it.

You'll never completely stop it, but you can slow it down.