Reoccuring 17748 - mapping tomorrow morning - FML

VAG-Slag

VAG-Slag

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Over the past week or so I've been slogging my guts out to get the car running with it's new engine and bits ready for mapping tomorrow...

Had an unbelievable amount of set backs as usual but just last night was able to get the car up to temp... Quick scan with vag-com and I'm getting a 17748 fault code.

-I've double checked the timing and it it 100% spot on
-I've tried 3 different cam shaft sensors, one of which I can garantee was working a couple weeks a go
-I've swapped out the crank sensor for one that was 100% working a couple weeks ago
-I've cleaned the reluctor ring for the cam sensor

I don't think it's a wiring issue as the the car has to be running for about 10 seconds before it comes on and same when you clear it, doesn't come back straight away.

Ross tech wiki mentions something about a potential oil blockage, but it's a brand new pick up pipe and I know oil is circulating...

Anyone got any ideas? I'll be gutted if I've thrown this much into the car just to not make it to mapping tomorrow....
 
17748/P1340/004928 - Camshaft Position Sensor (G40) / Engine Speed Sensor (G28): Incor. Correlation
Possible Causes
  • Timing Belt/Chain incorrectly installed
    • Timing Chain probably lengthened
  • Camshaft Position Sensor (G40) faulty
  • Engine Speed Sensor (G28) faulty
Possible Solutions
  • Check Timing Belt/Chain installation
    • Use Measuring Value Blocks (MVB) to Check Timing Chain
  • Check/Replace Camshaft Position Sensor (G40)
  • Check/Replace Engine Speed Sensor (G28)
Correlation error?
Physical check required to confirm if belts where it should be if sensors have been changed etc etc
 
So I just removed the VVT/tensioner to find the guide on the bottom with a massive chunk missing from it:


So I swapped it for the unit from my old engine, started the car up again and had a massive misfire... Basically somehow managed to kill a coil pack in the process there (!?) but it's ok, I has a spare!

Still getting 17748 though, even with the known to be working VVT/tensioner...
 
Should be popping into Bills around lunch time dude... hope to see you there

<tuffty/>
 
As said, I think it's an oil pressure issue so don't particularly fancy driving the 100 miles to bills at risk of buggering the rest of the engine... Which I could certainly do without!

Just gonna have to know when to call it quits I think :bye: However I will be back!
 
Usually doesn't that code pop up when timing is out by a tooth, engine will run but the ecu is clever enough to know its slightly out.

Did you set the crank 1 tooth before TDC then the tension lines it up correctly?

Its quite common if you google it and it happened on my mates Passat too, it was easier to see it there with the front end of the car off.
 
antwan64og said:
Usually doesn't that code pop up when timing is out by a tooth, engine will run but the ecu is clever enough to know its slightly out.

Did you set the crank 1 tooth before TDC then the tension lines it up correctly?

Its quite common if you google it and it happened on my mates Passat too, it was easier to see it there with the front end of the car off.
Click to expand...

I'm well aware of how easy it is to get these a tooth out. I've done literally almost 100's of 1.8t cam belts in the past, and never faulted on one before (or not one haven't immediately noticed anyway). . . This one I even did on an engine stand where everything is in plane sight.

I've checked time and time again since and all timing marks line up 100%... Unless my timing marks are out (!?), then this is not a timing issue
 
badger5 said:
physical tdc #1 in case bottom pulley keyway has sheared.
I never assume anything..
Click to expand...

I'll manually TDC it with the old 'long screwdriver down the plug hole' trick some point this weekend... However having worked on it until 10pm most nights for the past week or so I'm currently felling a bit over it to be honest!

Will keep this posted with any update though... Thanks for all input
 
sorry I wasn't doubting your mechanical ability, case markings can lie.

Good luck sorting it out
 
antwan64og said:
sorry I wasn't doubting your mechanical ability, case markings can lie.

Good luck sorting it out
Click to expand...

No offence taken, the mark on the pulley/belt cover obviously isn't exactly the most accurate system anyway! . .

Either way, just manually TDC'd (couldn't resist could I!) and all timing marks still spot on... Surely HAS to be an oil pressure issue, no?

I've actually got an oil pressure gauge already installed, I just need the adapter so the sender fits, which has been ordered. Soon as that turns up I'll be having a look at oil pressure
 
Further to this investigation...

The bits to plumb in my oil gauge turned up today so I've plumbed that in and I'm getting about 5 bar at idle from a cold start... Which is obviously ok

I've also cleared "learnt data" in vag-com and still no difference... The tensioner I swapped out does give a bit of a rattle on start up and as I shut the engine down, might try a new vvt tensioner but really I'd just be scraping the barrel a bit there. . . Apart from that it's generally got me completely stumped
 
By process of elimination it must be an erroneous electrical error somewhere.

Its mechanically lined up right.
Tensioner sees correct oil pressure so thats not knocking it out.

The ecu is seeing sync loss so it must be the sensors or the wiring.

Can you log the sensors in full vcds to narrow dow the culprit?
I'm not sure if you can
 
antwan64og said:
By process of elimination it must be an erroneous electrical error somewhere.

Its mechanically lined up right.
Tensioner sees correct oil pressure so thats not knocking it out.

The ecu is seeing sync loss so it must be the sensors or the wiring.

Can you log the sensors in full vcds to narrow dow the culprit?
I'm not sure if you can
Click to expand...

See, I'm now questioning whether the tensioner is getting good oil pressure as the one I swapped out didn't rattle on the old engine but now does on the new one... Maybe a blockage in the oil channel to the tensioner or something.

I have full VCDS however I'm not sure if you can log the signal in cvds, I might be better off reading the signal using an oscilloscope or something... Also, if it was a wire or sensor I'd expect an "implausibly signal" or "open circuit" type error.

Anyway, I'll get her rolling first and take it from there!
 
Last edited:
Last culprits I guess could be timing chain stretched beyond serviceable limit or the cam chain tensioner has gone (CCT but thats usually related to oil pressure apparently)
 
THIS IS DOING MY F*CKING HEAD IN NOW!!!!

So on top of the above I've now tried a different cam chain and different tensioner, both also known to be working...

And sill, 177fucking48!!! . . Completely out of ideas now

The only other thing I can think of is I used an ebay cambelt tensioner... Cambelt still has good tension though

Any other ideas before I go on a rampage and burn everything in sight?
 
bummer,
you mentioned earlier getting a scope on it (post 26), this would be the best way to see if there is a real deviation or if the signal is somehow getting corrupted, so at least it narrows it down to mechanical or electrical
/m
 
jaykay8L said:
Hope you find the issue.

Below link has quite a bit to say about oil pressure and the checking of. I think most cars will give higher bar reading for pressure when cold, its the when at operating temp that matters more.

http://www.audizine.com/forum/showt...essure-Survival-Guide-and-troubleshooting-DIY
Click to expand...

All cars will give higher oil pressure reading when cold because the oil is thicker. Oil pressure when warm is indeed usually more relevant, but not in this case. If I'm getting 5 bar when cold then that is more than enough to pressure up the tensioner properly.

Thanks for link though
 
it could be damaged wiring, you say that it takes 10secs or so for the fault to re appear when you clear it. I don't know the insides if these ECU's but its quite common to put a delay onto fault conditions before reporting them to prevent false alarms, maybe the great badger can confirm?

with all the engine work you've done its possible that a wire got nipped.

I believe the tacho is driven off the crank sensor which would point at the cam sensor wiring as being a suspect

really need to scope it at the ECU to prove this theory
good luck
 
newbster said:
it could be damaged wiring, you say that it takes 10secs or so for the fault to re appear when you clear it. I don't know the insides if these ECU's but its quite common to put a delay onto fault conditions before reporting them to prevent false alarms, maybe the great badger can confirm?

with all the engine work you've done its possible that a wire got nipped.

I believe the tacho is driven off the crank sensor which would point at the cam sensor wiring as being a suspect

really need to scope it at the ECU to prove this theory
good luck
Click to expand...

If it was a broken wire (i.e an open circuit) I would expect a completely different code all together... For example, if create an open circuit by unplugging the cam sensor I get a 16727 (Cam sensor - signal too high) and it wont even let me clear it.

Good thought though. . . Anyway, I'm going to get it properly back together and do some tests. I've spent long enough in the industry to have a good few mates with various diagnostic kits including scopes and stuff, see what we come up with!
 
Hello VAG-Slag,

Did you get to the bottom of it as I'm having the same problems, I'm thinking it's oil pressure?

Thanks
 
It was a piece of metal shaving in the oil feed to the cam chain adjuster left over from when the head was skimmed, probably got stuck in there while in the parts washer. It was preventing the oil getting through to operate the adjuster properly.
I had gone through checking the timming, cam position sensor, the engine speed sensor and I had replaced the oil pump prior to finding it.
 
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