Help interpreting VAG-Com output

n0brain3r

Hey all,

I've a 06 B6 Passat it went into limp mode today and the MIL came on. It was fine after a restart - MIL stayed though. It's gone into limp mode once before with no MIL and was fine after it was restarted. When I bought it - privately - the guy said he'd a problem with the Mass Airflow sensor and had it replaced showed me the recepits and a full service history so I'm happy enough that he was genuine and believed the fault to be fixed.

I've access to VAG-Com and have attached the readouts as txt files. I get their basic meaning but am wondering if it could be something more VAG1.txt from today shows 3 Glow Plug faults - probably nothing to do with my problem but could be a wiring issue seeing as it's in both readouts? Also shows a Mass Airflow Sensor - Implausible Signal and Altitude Sensor / Boost Pressure Sensor: Implausible Correlation fault can anyone shed any light? Are these sensors related? The MAF was replaced or at least I've a receipt saying it was replaced last December about 4500 miles ago.

In VAG2.txt this is from last month when it went into Limp mode with no MIL it reported the 3 Glow plugs and Manifold Pressure / Boost Sensor (G31): Signal too High.

Could this just be a case of faulty sensors? Or something more sinister?

Muckie

Don't know if this will help your case but i recently came across two Passts 01 and 04.

Both had very similar sound problems to yours.

Turned out to be the wiring loom connected to the coils.

Alanstrainor

Thread moved to tech help. You'll get a better response here i think.

n0brain3r

Muckie wrote: »

Don't know if this will help your case but i recently came across two Passts 01 and 04.

Both had very similar sound problems to yours.

Turned out to be the wiring loom connected to the coils.

Thanks Muckie did you get similar faults on a diagnostic? Do you know are these sensors on the same wiring loom as the coils?

n0brain3r

Ok I found these on the Ross Tech Wiki

http://wiki.ross-tech.com/wiki/index.php/16622/P0238/000568 for the fault code from last month for the Manifold Pressure / Boost Sensor.

http://wiki.ross-tech.com/wiki/index.php/18000/P1592/005522 this is the fault code from yesterday for the Altitude Sensor / Boost Pressure Sensor.

http://wiki.ross-tech.com/wiki/index.php/17416/P1008 is the closest I can get for the Mass Air Flow Sensor from yesterday.

All of them bar the MAF which isn't an exact match for the fault code I got suggest checking the wiring loom can anyone tell me where to look for these sensors? Does anyone know do they share the same loom? It also mentions corroded ground spots - I'm guessing the loom has terminations on the car body somewhere again any ideas?

Buford T Justice

n0brain3r wrote: »

Ok I found these on the Ross Tech Wiki

http://wiki.ross-tech.com/wiki/index.php/16622/P0238/000568 for the fault code from last month for the Manifold Pressure / Boost Sensor.

http://wiki.ross-tech.com/wiki/index.php/18000/P1592/005522 this is the fault code from yesterday for the Altitude Sensor / Boost Pressure Sensor.

http://wiki.ross-tech.com/wiki/index.php/17416/P1008 is the closest I can get for the Mass Air Flow Sensor from yesterday.

All of them bar the MAF which isn't an exact match for the fault code I got suggest checking the wiring loom can anyone tell me where to look for these sensors? Does anyone know do they share the same loom? It also mentions corroded ground spots - I'm guessing the loom has terminations on the car body somewhere again any ideas?

The Mass Airflow Sensor will be inline with the air intake between the air filter and the engine. Its a complete housing that the intake pipe plugs into and out of. That should get you started. you can check out vwaudiforum.co.uk and post there in the specific B6 forum there

n0brain3r

Ok I did a bit of routing around this evening I've uploaded 3 pics,

The first EngineBay.jpg shows my best guess at where each of the sensors are located maybe someone can tell me if I'm right? The other two are close ups of the sensors in in main pic. I've also marked a couple of pipes that where pinched by a plastic cover and are about 50% severed. Does anyone know what they are could they be related to the problem?

n0brain3r

Thanks fingers I didn't see your post I was uploading my huge pics! I'll try the vwaudiforum.co.uk from my pics do you think I've gotten the right sensors? I forgot to mention I pulled out the one I think is the Altitude Sensor / Boost Pressure Sensor and it was oily not much but enough to notice I'm guessing this is normal?

Slidey

You are right with the sensors.

The ones you have circled are correct.

Are the pipes worn through?

The oil would be normal enough in the pipe going from the intercooler to the manifold

n0brain3r

Thanks Slidey I was guessing based on google image searches!

The pipes are cut about half way through but not severed or leaking I don’t think much is holding it back though. I think they were being pinched until I removed the plastic cover from the top of the engine and noticed the damage.

Do you know what they're for it looked like one made its way back to the coolant reservoir so probably not related to my problem?

shamwari

n0brain3r wrote: »

Mass Airflow Sensor - Implausible Signal and Altitude Sensor / Boost Pressure Sensor: Implausible Correlation fault can anyone shed any light? Are these sensors related? The MAF was replaced or at least I've a receipt saying it was replaced last December about 4500 miles ago.

Assuming the MAF is clean, I reckon there is an air leak in the intake assembly somewhere. Worn pipes as you have already mentioned are a possibility. What will be a dead giveaway is if any of the pipes have oily stains around them - this will almost certainly mean that something is loose or damaged allowing air to ingress / egress depending on what the engine is doing. This will confuse the MAF (hence the code) and possibly manifold or boost pressure sensor.

Another potential trouble maker on some VAG engines are variable geometery turbos jamming in the max boost position, although they usuallf flag an overboost code when this happens. Again this can cause confusing MAF / MAP / Boost pressure codes.

One final thing is if the EGR valve is lazy when closing as this will cause anomalies in the airflow which again can confuse the MAF. This will cause flat spots and the occasional belch of smoke...:D

shamwari

Actually just looked at your photo's. I'm wondering if your car has been fitted with the correct MAF. Cleary wires have been cut, possible to change the plug to allow a different MAF fit.

Can you read correct live data from the MAF using VAG-com? If so, can you post airflow readings from the MAF with the engine at
(a) tickover
(b) a constant 2000rpm and
(c) a constant 4000rpm?

Also what make is that new MAF?

n0brain3r

Air flow at idle is 220-240 mg/str
at 2000rpm - 260-280
at 4000rpm - 520-540

The MAF has VW markings on it so I'm guessing it's VW.

shamwari

OP

Those units (mg/str) are milligrams per stroke. There are wildly different ways reported on converting this metric (Kg/hr or grams per sec). Is it possible to change the units in VAG com to metric / time and report them back? Sorry for the added hassle but I'm not used to working in those units!!!

Also, what RPM approx is your tickover?

And does the car drive normally with good consistent power, or it is sluggish?

n0brain3r

Ticking over is 899rpm from memory. The car drives perfectly when not in limp mode no sluggishness and power is consistant - It passed it's NCT today too! No smoke or rough running it seems perfect. I'll see what I can do with VAG-Com tomorrow(The Baby is asleep now ) What units of measurement do you need? Is it litres per sec?

shamwari

n0brain3r wrote: »

Ticking over is 899rpm from memory. The car drives perfectly when not in limp mode no sluggishness and power is consistant - It passed it's NCT today too! No smoke or rough running it seems perfect. I'll see what I can do with VAG-Com tomorrow(The Baby is asleep now ) What units of measurement do you need? Is it litres per sec?

KG per hr or grams per sec are the unit's I'm used to dealing with.

I looked further into it last night and found some formulas in an old text book. I don't have the calculations to hand now but assuming I got the maths right, your airflow values appear to be about correct, so don't worry too much. Incidentally I based your tickover speed on 900rpm so I was at or about right with that!

Getting back to the error codes relating to airflow and boost, I still feel that the likelihood is that there may be an air leak somewhere in the system OR the wiring near the MAF connector is iffy and corrupting the signal. It might be no harm to recheck these.

Also, is there a freeze frame of data when the error occurs? If so, what are the readings in the freeze frame, particularly regarding airflow and boost / manifold pressure?

n0brain3r

000257 - Mass Air Flow Sensor (G70): Implausible Signal
P0101 - 000 - - - Intermittent
Freeze Frame:
Fault Status: 00110000
Fault Priority: 0
Fault Frequency: 1
Mileage: 133726 km
Time Indication: 0
Date: 2000.00.00
Time: 11:16:43
Freeze Frame:
RPM: 2205 /min
Speed: 103.0 km/h
Temperature: 19.8°C
Absolute Pres.: 1519.8 mbar
Mass Flow: 36.98 g/s
(no units): 1.22
Temperature: 82.8°C
005522 - Altitude Sensor / Boost Pressure Sensor: Implausible Correlation
P1592 - 000 - - - Intermittent
Freeze Frame:
Fault Status: 00100000
Fault Priority: 0
Fault Frequency: 1
Time Indication: 0
Freeze Frame:
RPM: 0 /min
Speed: 0.0 km/h
Pressure: 254 mbar
Pressure: -256 mbar
Bin. Bits: 00011010
Absolute Pres.: 999.6 mbar
Absolute Pres.: 1458.6 mbar
Readiness: 1 1 0 0 0

Is this the freeze frame your looking for? I'll try get time at the weekend and go through the wiring and air system and see if I can find anything. Thanks for the help

shamwari

Ok, those two freeze frames are taken at different times.

Frame one associated with Airflow correlation error is a little odd. It is showing an airflow of 36.98 grams which is possibly a little low for a car doing 60mph in top gear, but not enough to cause an error inself.

Frame two is unrelated insofar as the engine is stopped (0rpm and road speed). Therefore it cannot be a boost problem per se as there will be none. This may be sensor or wiring.

Can you confirm the year and engine code of your passat if you know it. If you don't know the engine code, do you know the bhp? I'll see if I can dig out a wiring diagram for your engine and see if there is possible a common cause from a wiring point of view.

n0brain3r

It's an 06 and the engine code I think is BXE it doesn't list the HP but shows the power output as 77KW & engine variant TDI SG5.

I'll try download the freeze frames again tomorrow but I cleared the faults for the NCT to clear the MIL so I don't think anything will be left.

Esel

Fwiw, KW/0.746 = BHP, so 77 KW = 103 BHP

shamwari

Feck...my Autodata doesn't have a wiring diagram for the new passat.

When you cleared the fault codes to put out the light after the NCT, did the fault reoccur since?

n0brain3r

Nope it's only happend 2 or 3 times in the 5000 or so miles I've had it and switching the car off & key out allways takes it out of limp mode it's just a pain not knowing what exactly is causing it :mad:.

If it stops raining here I'm going to try trace the wiring loom it disappears down the side of the engine block out of view so I can be sure it's intact. The MAF cut and spliced connections look good I might tape them up too incase it getting damp has anything to do with it.

The first freeze frame for the MAF did you find out if that was a normal reading?

shamwari

n0brain3r wrote: »

Nope it's only happend 2 or 3 times in the 5000 or so miles I've had it and switching the car off & key out allways takes it out of limp mode it's just a pain not knowing what exactly is causing it :mad:.

If it stops raining here I'm going to try trace the wiring loom it disappears down the side of the engine block out of view so I can be sure it's intact. The MAF cut and spliced connections look good I might tape them up too incase it getting damp has anything to do with it.

The first freeze frame for the MAF did you find out if that was a normal reading?

As I said, the airflow reading from frame1 is a little lower than I would expect, but should not cause a problem. If it did, you'd notice it under the right foot. I've had similar problems to yours with another car and there was an air leak in the intake. Oily marks around the intake pipework were the giveaway.

n0brain3r

Thanks shamwari, I'm having no luck with the car the NCTS helped destroy a perfectly good tyre and some fwit stole the wing mirror on sunday :mad: . I'll go through the pipepwork some evening this week. I'm gona trace from the air filter to the engine right? - Sorry for the stupid questions

shamwari

n0brain3r wrote: »

Thanks shamwari, I'm having no luck with the car the NCTS helped destroy a perfectly good tyre and some fwit stole the wing mirror on sunday :mad: . I'll go through the pipepwork some evening this week. I'm gona trace from the air filter to the engine right? - Sorry for the stupid questions

Yes, air filter, through maf and then into the turbo.
Output from turbo goes thru intercooler and then into inlet manifold.

Esel

esel wrote: »

Fwiw, KW/0.746 = BHP, so 77 KW = 103 BHP

Just another way of doing this calculation: KW*1.34 = BHP, so rough mental calculation is to add 1/3 to the KW figure. Easier, if very slightly less accurate.

n0brain3r

shamwari wrote: »

Yes, air filter, through maf and then into the turbo.
Output from turbo goes thru intercooler and then into inlet manifold.

Ok I checked from the air filter through the MAF and into the turbo which is at the back of the engine right? Then from what I'm guessing is the turbo around to the front of the engine around the dip stick (See pics on first post)and down to the intercooler beside the radiator?

From what I can see everything looks good. I can't see where exactly the intercooler is I think I'll need to look from beneath & need to remove a plastic sump guard to do it.

The air intake from the front of the car to the filter wasn't correctly assembled but I'm guessing as this is before the air passes the filter it's irrelevant. Also a couple of the screws holding the top on the filter missed their sockets and where holding the lid slightly ajar.

I’ve attached a pic of I’m not sure what but it’s covered in oil and it’s a bit far from the filler cap to be a spill evidence of a previous problem or related to this one maybe?

Thanks again for all the help.

Esel

You used black text on that post, which is invisible to users on the Cloud skin (this has a black background, so - black on black....). It's best to stay with the default font colour, imo.

shamwari

n0brain3r wrote: »

Ok I checked from the air filter through the MAF and into the turbo which is at the back of the engine right? Then from what I'm guessing is the turbo around to the front of the engine around the dip stick (See pics on first post)and down to the intercooler beside the radiator?

From what I can see everything looks good. I can't see where exactly the intercooler is I think I'll need to look from beneath & need to remove a plastic sump guard to do it.

The air intake from the front of the car to the filter wasn't correctly assembled but I'm guessing as this is before the air passes the filter it's irrelevant. Also a couple of the screws holding the top on the filter missed their sockets and where holding the lid slightly ajar.

I’ve attached a pic of I’m not sure what but it’s covered in oil and it’s a bit far from the filler cap to be a spill evidence of a previous problem or related to this one maybe?

Thanks again for all the help.

That item in the photograph looks like your fuel filter. When these are being replaced, it may be necessary to disconnect some of the pipe work and this can result is a small spillage of diesel, hence the oily look of it. If there was a problem with it, you would have more serious running problems, and it would not cause your MAF fault.

Also if the intercooler was holed significantly, the car would be quite noisy to drive, particularly under hard acceleration so I would not worry about looking there.

shamwari

OP, I think I might have spotted something I looked at some time ago but discounted on the strength of the live data.

I've attached a photo you took off your MAF, and I am beginning to think that the MAF in your car might not be the right one after all. It is clear from the photo that the MAF and it's plug were changed as there is a clear difference in the colour of the wiring. The correct MAF should just be plugged on without its plug being replaced.

Can you get any numbers off the body of the MAF and I'll check see if I can find what car(s) it is supposed to fit. Even though the MAF is producing an output which is readable by the ECU, its characteristics and output under certain operating conditions might confuse the ECU and cause it to throw a fault code.

n0brain3r

Ok I got two sets of numbers the first set were quite hard to make out(Might not be right) and on the body of the plug 110 973 999 the second set were on the body of the maf 0 281 002 531.