P0299 - 006 - Control Range Not Reached - Intermittent B6 Passat

[martin1810]

Has the map sensor been replaced. It could be giving the ecu faulty readings. You problem should not be stuck turbo vanes because they stick at the high boost point and so give an 'overboost' code. They can only give an underboost code if you start and continue to have 'low boost'. Either the MAP sensor is telling lies or you have a vacuum leak which only occurs when driving. As I said before, the ecu behaves differently when the car is stationary so driving faults can occur only when driving. I'm not certain which flap valve you are talking about. (which diagram number) The antishudder flap (part of egr) or manifold flap (in inlet manifold). I guess you mean the inlet manifold flaps which change air supply during driving. These are a common failure. Do you have an error code for them? Usually upper stop or lower stop not reached.

[silversimpson]

Has the map sensor been replaced. It could be giving the ecu faulty readings. You problem should not be stuck turbo vanes because they stick at the high boost point and so give an 'overboost' code. They can only give an underboost code if you start and continue to have 'low boost'. Either the MAP sensor is telling lies or you have a vacuum leak which only occurs when driving. As I said before, the ecu behaves differently when the car is stationary so driving faults can occur only when driving. I'm not certain which flap valve you are talking about. (which diagram number) The antishudder flap (part of egr) or manifold flap (in inlet manifold). I guess you mean the inlet manifold flaps which change air supply during driving. These are a common failure. Do you have an error code for them? Usually upper stop or lower stop not reached.

The MAP sensor has been replaced. It seems like the diaphragm has split in the manifold vacuum unit (part 9 on diagram therefore leaking vacuum to the outside world whenever the intake manifold flap air flow control valve -N316- (part 7) decides it needs to supply vacuum to it. I have blanked off the vacuum supply hose and eliminated control vacuum to part 9, therefore bodge curing the vacuum system leak. It still goes into limp mode, and I am now hoping that by replacing part 9 on Tuesday/Wednesday this week (fixing it properly), it may cure the underboost problem (see link B7 Tdi 170 Avant, low boost issues (post 6 on the page from Audi_Diesel) which I think is the same problem). There is no other error code on VCDS other than the title of this thread.

[martin1810]

Yes that would do it. A leak in the change over actuator or the egr actuator could occur when driving but not at standstill and so cause limp to suddenly occur while driving. You could try blanking off the piping for the egr and manifold flap actuator by plugging the pipes as near to the turbo vacuum line as possible, therefore eliminating both of them and their pipework. A golf tee or smooth bolt pushed into the vacuum pipes usually works ok. This will probably cause fault codes when you drive but should establish where the fault is. You can always clear the codes later. Don't forget while playing with vacuum pipes that a sudden loss of brake servo vacuum may give you a heart attack on the road so consider that when testing on the road.

[silversimpson]

Should fit the new part on Wednesday, I'll let you know how I get on. On holiday in Cromer next week if the car gets us there!

[silversimpson]

Hello again, had new spark of enthusiasm! Replaced the manifold flap actuator and had EGR/Throttle valve de-coked, no joy. Saved up for turbo refurbish and replaced, no joy. blanked off all vacuum systems but the n75/Turbo and the brake servo, no joy. VCDS graph of boost specified against boost actual shows that boost falls short of specified. Car generally has low power (even when not in limp mode, which it goes into fairly frequently). Is there anything else to try? Please help.

[johnnybeast]

Hello, I was just reading through these posts about your underpowered Passat.

I too have a BMR engined Passat with a very similar problem. I was wondering if you have come any closer to finding the issue? Have you changed the fuel filter recently? That made a large improvement to my engine's performance and it doesn't slip into limp mode as much as it did before... but it still does!

J.

[silversimpson]

Hi J,

To be honest, I have not yet got to the bottom of it. I tend to pluck up some money and enthusiasm over a period of around 2 months while driving my trusty Mk4 Golf 130tdi (237,000 miles so far), then have a go at something else! The latest tip I have been given by an ex VW man (through a friend of a friend) having provided him with some readings off VCDS (can't remember what they were but will try to find them) he said that 'some things didn't add up' and to check the earth connections around and under the battery area as this had shown up as an issue in the past on other cars. His other suggestion was that the wiring loom in that area (sorry don't know exactly where) had also been faulty on a car he had seen before. I will check all earth connections that I can find in the near future for sound connection to start with. If this does not reveal any issues, I will look at the wiring loom, but unless there is any visible damage, although I am an electronics engineer by trade, not knowing what signals should be on the wires will make things extremely difficult to diagnose. I can only think that it is now down to an electrical gremlin somewhere which could be in the wiring or ECU (I've changed, tested or cleaned everything else to my knowledge). I could just bite the bullet (admit defeat) after all this time and take it in to VW in Derby and leave my cheque book at the mercy of a master technician, but I'm not that convinced that they could help either. I feel that I have just been urinating into the wind with my efforts so far, although I have learnt a lot about the engine (far more than I wanted to) and have managed to fix a couple of things along the way. Will post more when I have done something else, but would appreciate any further advice. Feel like Basil Fawlty thrashing his car...

[johnnybeast]

Hello again,

Just letting you know I've found (and temporarily fixed) the problem with my underboosting engine! Hoping it will help you out, or give you something to have a look at.

My problem was with the plastic intake manifold (03G129711AF) where the leaver for the butterfly flaps exits the left side of the manifold. The leaver is attached to a vacuum operated actuator. The bush or seal or whatever was there originally, wasn't anymore. The gap around the leaver is only small, but when you're talking about a peak of 2.5bar a small hole is big enough.

Apparently it happens to all the older plastic intake manifolds on the BMN and BMR 170bhp engines (03G129711AF and 03G129711AP) the seal breaks down over time with heat, movement and pressure and disappears.

To replace the manifold with the new modified version (03G129711AS) will set you back a good £500 or so. All I have done at the moment it cut the flaps out, pulled the bar out and sealed the hole with some plastic, silicone and a nice self-tapper which has done the job nicely! I 'modified' it to see if that was where I was loosing all my boost - now to start saving for a new one. I did contemplate a second-hand manifold, but at the cost of £200 for something that will break at some point anyway I've decided to bite the bullet and start saving!

It's boosting like a trooper now, a completely different car, more power, response and economy : )

Here's a video I took of the manifold when it was off to show the problem - http://youtu.be/-51Mcw3CGtU

Hope it helps, keep me posted.

Seriously happy,
J.

[silversimpson]

Hi J,

I have just gained enough enthusiasam to have another go at the Passat (I haven't really used it for months)! There is no issue with my inlet manifold (other than the actuator that moves the butterfly flaps, which I have already replaced due to a vacuum leak) like you show in your video clip, but many thanks for that. I have (last Thursday) taken the car now to VW Parkway in Derby and admitted defeat! Haven't got the car back yet as I have been informed that so far 'diagnosis has been inconclusive'! That (in a weird kind of way) makes me feel that this is a really tricky problem and I don't feel so bad about not tracking it down now! So far they have said that they cannot do a dynamic boost control range test (or something along those lines) because as soon as the engine gets higher up in the rev range, the engine slips into limp mode (I could have told them that!). Apparently there are a couple of pressure readings that need to be within 50mBar of each other, and on my car this is exceeded. The master tech's tech notes tell him that he is to replace a section of wiring loom (I think the one that connects to the MAP sensor, this was eluded to earlier in this thread but no action taken at that time) and re program the ECU with the latest software (quoted £350 with a waiver of the £80 diagnostic fee). I don't know if the re-programming is necessary for this fix, but if it is I suspect poor design. Anyhow, I think they have now replaced the loom section and proceeded to pre-program the ECU…which failed. Since then the master tech has been doing some 'extensive wiring checks' to which he has found corrosion on the connections to the ECU. Tomorrow he is going to fit some new contacts to the connector and have another go at the re-program. I wait for tomorrow's conversation with eager anticipation (170 horses back). Despite my tone, I am getting the feeling that the master tech might be getting to the root cause of the fault, and for that I have a smidgen of hope...

Mike.

[martin1810]

Did you ever manage to graph your boost pressure whilst driving? You mention it in the first post but there is no log attached. The VW tech should be able to check and compare sensor signals. You can do this with a multimeter but you have to be driving and VW don't give any specs for the values. It is usually possible to work out specs once you have some raw data. Have fun. VW wires and connectors seem to be poor quality on the B6 judging by broken wires and corroded terminals.