V70: General P029900

[RM955I]

Hi, It's been several years since I've posted as having moved from a P2 to a P3, the P3 D5 (twin turbo) has been almost faultless - it has been superbly reliable in every sense.

It now has 195,000 miles on it and what started as an intermittent fault is now pretty permanent - "engine system service required". It's not the common oil level issue, as I have checked and re-checked that: I have an icarsoft reader reporting "P029900 underboost" telling me it relates to part 31269213 AB.

Before I start throwing money at parts can anyone give me any pointers on things to clean/check/test.

I have cleaned the MAF with electrical contact cleaner (no residue), the fuel filter was changed recently, the air filter was changed. At that age and mileage, it's not worth spending hundreds of pounds chasing faults and buying parts that may or not fix it.

The iCarsoft ain't no VIDA/DICE but it can give live data streams and reads all modules, so any input on what to check and what I'm looking for would be helpful - thanks

[Kev0607]

Ideally, you need VIDA/Dice to read the codes properly. The generic scan tools are pretty much useless, as many of them can't clear the fault code even if you fix the issue.

I would suggest checking the intercooler to see if its cracked, aswell as checking all the rubber hoses for any splits because they perish over time & can cause leaks/boost issues.

[RM955I]

Thanks...probably worth saying that the iCarsoft is Volvo specific, does read all modules and it's not a generic reader.

It's not quite as good as VIDA/DICE (eg resetting transmission adaptations) but it will give detailed fault codes, read live data streams across various sensors and even suggest part numbers as well as clear faults.

I have visually checked hoses but will have a good look at the intercooler too.

[Kev0607]

You learn something new every day as they say.

Info from VIDA, this may help;

"ECM-P029900:
The Engine control module (ECM) regulates the turbo pressure using a turbo control valve.
The control module can detect small faults in boost pressure regulation over a longer period of time and larger faults in a shorter time.
The diagnostic trouble code (DTC) is stored if the control module detects that:
The actual turbo pressure is less (approx. 15 kPa for 10 seconds) than what the Engine control module (ECM) regulated (maximum regulation achieved).
The control module's test for the diagnostic trouble code (DTC) starts in the event of:
Normal load (driving).
Boost pressure (approx. 30 kPa above atmospheric pressure).

Possible source
Damaged turbocharger (TC) control valve.
Air leakage in the intake system.
Damaged turbo charger (TC).
Damaged relief valve.
The hoses between the turbo control valve, wastegate and its corresponding pressure servo have come loose, become blocked or damaged.
Sticking boost pressure control (BPC) valve.
Damaged boost pressure control (BPC) valve pressure servo."

[RM955I]

I started with the obvious of changing the fuel filter - it wasn't due but for the sake of £10 from GSF, it was logical.

Next was the TMAP sensor as I recall someone mentioning it - it was pretty much totally encrusted with baked-on gunge. I carefully picked away as much from the surround as possible, avoiding the sensor.

What I did next may horrify some...but it worked. I put it in an ultrasonic cleaner, being careful only to immerse the probe and nothing else...and filled it with 'Gunk'. After about 20 minutes and several changes of Gunk, I sprayed with electrical contact cleaner and allowed to dry overnight.

So far, no 'Engine System Service required' warning! Let's hope it stays that way as chasing down this problem seems to be a game of chance.

[RM955I]

It's back.

The fault code is the same. I can't help but wonder whether the TMAP sensor is knackered. There is no loss of power, no MIL (just the engine system service required message), no erratic idle, no excess fuel consumption - the car runs perfectly normally.

I admin to not really knowing what I'm looking for but what does strike me is that the manifold pressure hardly moves from tickover to 3000 revs, whereas the boost pressure clearly does rise.

Any ideas please....anyone And can anyone confirm that the TMAP is the lower right, not the upper left circled? (sorry - pics are wrong orientation when I upload but fine on my pc)

I might have to take this to a specialist...or ignore it: the car is not worth chucking hundreds of pounds at - it's 10 years old with 195,000 on it and this problem seems to have so many possible causes.

Thanks

[Kev0607]

Have you checked the intercooler to see that it isn't leaking or coated in oil? Also, check the hoses around the intercooler & turbo for splits/cracks. Check the TCV (Turbo Control Valve) & give that a clean with electrical spray too.

As you say, there's many potential culprits. As the MAP sensor was full of gunk & you cleaned it the best you could, there's a possibility that the sensor could still be at fault though because goodness knows how long it was clogged for. Check the above & if they seem okay, then replace the MAP sensor (Lower right in the pic you posted & the part number is on it if you look closely).

[RM955I]

Looking for the location of the 2nd sensor on the intercooler...buggered if I can see it! I have a sneaking suspicion it's a bumper off job but I can't see it, unlike this video which admittedly is for an XC60 D5 - not sure what year but it's a twin turbo, so should be the same.

In the picture that's the air intake on the right, slightly blurry; radiator to the left. All I can see is what looks like a cooler for the transmission?

[Kev0607]

Is it the TCV valve you're looking for? If so, its near the air filter box on my car, close to the slam panel at the back of the headlight. I'm not sure if your car will be the same, but have look there.

This video below is for a euro 3 car. My TCV is in a similar place on my car, but its closer to the headlight than this. You can see there's a gap between the TCV & the slam panel/body in this video, but mine doesn't have as much room as this being a euro 4. Its more or less in the same place though, just closer to the back of the headlight area.

https://www.youtube.com/watch?v=qvpjhN-2DdI

[Xanova]

Hi, i have the same fault. Did you solve it? Thank you