HELP! P029900 Turbocharger Underboost

[jrpowney]

Hi,

I've had my 2011 1.6 Maxi for about 3 weeks now and the other day the engine management lamp started flashing and the van lost power.

I've ran it through my code scanner and it came back with - "P029900 Turbocharger/Supercharger Underboost Passive/Abiogenesis". I've rang my mechanic and he reckons it's the turbo wastegate but can't be sure until it completely breaks (I don't want to wait for that to happen).

The problem only happens when I'm going around 65-70mph on a motorway. It will make me change down gear and go around 40-50mph. I can push it back up to around 60-70mph downhill and then keep it going on the flat.

Has anyone had this problem before or could help me figure out what's causing it?

Cheers
Jake

[Doc]

Hi, welcome to the forum.

Have you checked all your intake pipes and connections to make sure there are no leaks? A boost leak is the most likely cause of underboost.
There may also be a restriction on you air at the filter or MAF, check that also.
Do you have any whistle noises from under the engine while you drive on boost?
Your turbo is a variable vane type with no wastegate so it definitely won't be that.

[p1andy]

Had the same symptoms and fault when I bought the van last year. I searched all the vacuum system and replaced a couple of valves with no luck. Turned out to be the actuator on the turbo had a burst/fatigued diaphragm. £50ish for a new one and a few hour swearing to change it out.

[jrpowney]

Had the same symptoms and fault when I bought the van last year. I searched all the vacuum system and replaced a couple of valves with no luck. Turned out to be the actuator on the turbo had a burst/fatigued diaphragm. £50ish for a new one and a few hour swearing to change it out.

Is there anyway to check if the actuator has got a burst/fatigued diaphragm or is it a case of taking it out to look?

[jrpowney]

Hi, welcome to the forum.

Have you checked all your intake pipes and connections to make sure there are no leaks? A boost leak is the most likely cause of underboost.
There may also be a restriction on you air at the filter or MAF, check that also.
Do you have any whistle noises from under the engine while you drive on boost?
Your turbo is a variable vane type with no wastegate so it definitely won't be that.

I have got a leak, but I think it's one of the injectors (If i'm correct, big newbie over here).



There's no whistle that I can hear, the van just has no power behind it.

[Doc]

Hmmmm, nah an injector leak won't cause underboost.
How about the air filter and the pipework between that and the turbo?

The turbo actuator diaphragm can be tested with a vacuum test tool, most good garages should have one.

[p1andy]

As above, try borrow a shot of one from a garage. I bought one as was only +/-£25 and will come in handy.