Hi all

2.0TDI Octavia scout, 2011. CFHC engine. About a month ago I got an odd whining noise while driving, increasing as revs did. I drove slowly home and it got a bit quieter. Got it to the garage, and they told me a bolt had fallen out of the water pump and got dragged around in the cambelt. Mechanic showed me a pic, and the timing cog on the end of the camshaft or crankshaft (whichever one is at the top of the engine!) had had one edge worn away - plenty of meat left on the cog though. Mechanic cleaned it all up, put new belt, rollers and idlers on, and it ran fine. However, when I tried to restart it while hot, it would immediately conk out, with a flashing coil light and the message "Engine fault. Garage". I put a fault code reader on it, and got "Bank 1: CMP sensor (G40) Engine speed sensor (G28): Incorrect correlation P0016" - but the car would always restart after a few minutes to cool down, or if I turn on or off the air con, open the bonnet etc. Once running it runs fine. Clearing the fault code makes no difference. Sometimes it conks out on starting (only when hot) but no fault code is found, and the "engine fault" message doesn't display.

Back to the garage I went, and the mechanic ran his fault code reader over it, googled the fault code, and said it was probably down to the missing edge on the camshaft timing cog. He said a new one would probably be needed (6 hours labour or so), possibly even a new crankshaft or camshaft if the cog isn't available on its own. The latter would be around 4k total, so the car would be written off. Argh. I said isn't it more likely just to be one of the sensors having a hissy fit? he said probably not as they wouldn't have been disturbed by the cambelt replacement. We agreed that he'll have the car back and take the belt cover off again and see if there's anything obviously amiss or if he can adjust it slightly and make it happy. I'm inclined to ask him to clean or even replace the sensors (Crankshaft Position Sensor (CKP) or Camshaft Position Sensor (CMP)?) while he's in there, on the chance it'll save me another £400 bill, or possibly a 4k bill!

I'd rather not scrap the car, it runs well when it's running, and is generally sound. 141k miles, though it has been a bit less reliable recently. Had it serviced 2 months ago, of course!!

Anything else I could get him to check while he's there, hopefully easier and cheaper fixes?

Thanks for any suggestions.

Just to add, the check engine light has never come on. And the mechanic is sure he got the new timing belt on properly, all the pins lined up correctly, etc.

Logic suggests that a correlation error is not a fault with either sensor (which would have dedicated and specific fault codes) but a strong hint that the belt has not been fitted correctly, and the engine is mis-timed.

Maybe the garage has used incorrect locking tools?

Hmm. The engine runs nice and smoothly when it's running. I believe the locking tool was new... But it does seem an odd coincidence...

On 01/01/2026 at 04:01, Breezy_Pete said:

but a strong hint that the belt has not been fitted correctly, and the engine is mis-timed.

Id say this 100%

Get mechanic to retime correctly.

I think these engines have floating pulleys so lining up the marks is only half the job. Not as simple as older belts.

Have to lock crank and cam and tension with pulleys floating then fix pulleys.

Thanks. Back at the garage on the 13th, I'll get him to check everything again. I'll mention floating pulleys!

Given that it seems to run fine should I not drive it in the meantime?

On my 1.9tdi it was the same. You had to loosen pulley slightly to get timing just spot on. When I used the locking tools and then rotated engine once belt was fitted it was just slightly out after a complete turn and I couldnt get locking pin back in again without loosening pulley. It only moved about 1mm but that was enough to line everything up. If it was a sensor then I am sure a code would have been stored.

Not sure re driving but its probably only slightly out so may be ok. Personally I wouldnt if possible until you get it checked in case its the tensioner/belt thats been wrongly fitted.

Alasdair

Thanks Alasdair, that's helpful. I'll pass it on. Seems to be driving fine so far. And I've already driven it a few hundred miles since the belt was done!

If its the top timing cog then it looks like this.

You can see the elongated holes that alow for adjustment. I came up with part number 03L 109 111 but you would have to double check. There are a few on ebay for £15-£20 or new from skodaparts.com genuine for £50 but I cant see it affecting timing unless its needing adjustent or possibly moved slightly. Not sure where the 4k bill comes from unless hes completely dismantling engine and rebuilding. Hope its an easy fix

Alasdair

Thank you Alasdair, that's very helpful. Cog looks right, but I'll double check. Yeah, the 4k bill was to basically dismantle the engine to potentially replace the whole camshaft. Looks like that wouldn't be necessary as the cog comes separately, but I still can't see how a worn edge to it would affect timing. My suspicion is that the mechanic has got it slightly off.

I agree unless its badly worn or damaged but if its just the edge I cant see it affecting timing. Reckon your suspicion is correct. It shouldnt be too big a job to remove covers and check. Make sure the garage uses the correct tool for the 2.0tdi

Alasdair

In the pic he showed me, about 5mm of the cog was worn, on the block side. But a good 3/4 of the width of tooth was still there.

Hard to find a garage I can trust!

9 minutes ago, sandspider said:

Hard to find a garage I can trust!

I know what you mean. I do all my own if I can. Used to have an excellent old school garage but Robert retired a couple of years ago. With the two mechanics plus his son and himself they had over 100 years of experience added together. He was finding that modern cars were requiring more and more expensive diagnostic euipment and tools. Shame its gone but I understand why. Maybe someone on here could reccomend a decent one in your area.

Alasdair

I had the belts done last time at a garage recommended from here (as far as I remember anyway), in Bath. According to my current garage they didn't do a great job - bolts missing from the waterpump, not tightened up etc. Hence a bolt getting into the cambelt recently. But it was 4 years since the belts were done by that garage, so might just be bad luck...

I get a random bolt coming loose although if its torqued properly shouldnt but it happens. Bolts missing on the otherhand is not acceptable at all. Far to many garages miss them out or dont torque properly. Years ago I had a clutch problem that a small so called good garage fixed for me. Next time I was in my preferred garage now retired they pointed out that only the bottom bolts on the bellhousing were tight but the others were loose with two missing plus a few cables etc had not been reclipped securely. Even good garages can have poor mechanics.

Hope you get it sorted.

Alasdair

It's hard to know for sure of course- I've only got the new garage's word for it. 🤷‍♂️

Thank you.

Bit late to the party but just to say that I also think this is a timing issue. They are pretty fussy about it. Different animal I know but have had a very similar problem on a 1.9PD which was completely fixed by simply re-timing it. Also of note was that the timing kit I borrowed for this had several combination of tool that appeared to fit but only one that was actually right! Working out which was the chore.

Also have to wonder when they are apparently happy to quote £4k to change the pulley which they previously thought was ok..... especially when (as Alasdair has already pointed out) the pulleys are really not expensive.

Good luck!

Thank you. Hopefully it's just that simple, and they don't charge me any more if they got it wrong the first time! I'll tell the mechanic he's done it wrong 😀

And the 4k was to possibly replace the whole camshaft, much engine dismantling required, not just to do the pulley...

Maybe go softly and tell the mechanic that you think the timing is slightly out due to the fault code and info from members here and you would like them to recheck it rather than tell him he got it wrong. Last thing you want is to annoy a mechanic/garage etc and have them working on your car. If he gets stroppy then you can take the complaint up a level or two.

Good luck and hopefully a re time will cure the problem.

Alasdair

Ha, I wasn't actually going to tell him he'd done it wrong, I was going to be more subtle! As it happens he's had an accident and broken himself, so he can't look at the car again until the 19th now anyway. Darn it. It no longer starts all the time from cold either ☹️

Thanks again Alasdair.

Maybe give it another scan in case theres any other codes stored. Nothing worse than a car that wont start all the time. If it was starting ok before belt change then chances are its something mechanic has done. Hope you get it sorted soon

Alasdair

You mentioned going to Bath to visit a good garage; whereabouts are you? If you're on the Bristol/Newport side I can recommend a very good garage. Might be too far if you're on the other side towards Reading, though.

I'm near Chepstow. So Bristol / Newport are all doable. Where do you recommend? Thanks.

In that case I'd definitely recommend GL Autos in Cwmbran. Proper family garage, good workmanship and decent prices.

Thanks Jamie, I'll look into them.