ESC, TPMS, Start Stop & Engine Management Issue

Dec 13, 2021
3
2
Northern Ireland
Hey all,
Longtime reader, first time poster. I’ll cut to the chase. I have a 2016 DSG Leon Estate with the Technology pack.

Seemingly at random, when cold, the gears will change extremely sharply and when keeping pace in D5, will periodically drop to D3 and back up to D5 again, with no change in speed. Additionally, also seemingly at random either as soon as I set off or after driving for a few hours, the ESC warning light will flash, accompanied by a message saying Error: ESC System, which then triggers the TPMS warning light to flash accompanied by a similar message saying Error: Tyre Pressure System (or similar, can't recall from memory). With Start-Stop on, after these errors appear, when coming to a stop, another error message appears "Error: Start-Stop System". If I turn start-stop off, the ESC and TPMS errors still occur.

The above is manageable, I can turn the car off and back on again and the errors will vanish. However, at times in addition to the error lights above (or even without them) the glow-plug system light will flash (apparently this is the engine management light in these yokes?) When that happens, if I'm at a stop and go to move the car the mini display between the speedometer and the rev gauge will alert me to "Manually start the engine", when I do so and go to move off again, the engine cuts out once more. I need either a full turn off and remove the key(Cumbersome when literally on a roundabout) or to put it in semi-automatic to get it to stay turned-on.

So those are the symptoms, here's what the dealer I bought it from has tried;
Checked it using an OBDII scanner (Results also attached or read online by clicking here)
Checking the TPMS error was actually an error and not just a normal activation for low pressure
New battery
New Fuel unit

It was then sent to someone who specialises in rebuilding these gearboxes due to the symptoms shown by the sudden sharp gear changes and they couldn't find anything wrong with the gearbox or on inspection of anything that they believed would cause the fault codes shown in the diagnostic. I had also read on this forum or perhaps somewhere else that a likely cause could be a faulty ABS sensor which even with a full service history is unlikely to ever be replaced/looked at, at 100k miles (163k KM) this seemed plausible so I mentioned it to the mechanic but he's just off the phone with me saying he can't get it to happen for him to diagnose.

The only other issues that may or may not be related are that when idle, the engine shakes a lot and the fuel pump is quite audible.

Any ideas?

P.S Sorry for writing a book.
 

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Woody_72

Active Member
May 10, 2020
497
245
Northwest England
You're right to mention wheel speed sensors as these are involved it the TPMS system and the ESC system to detect wheel speed. I'd be inclined to start by jacking each corner up, popping the wheel off and have a really good look at the wheel speed speed sensors ie check for fraying, rodent damage or green crusties in the connectors themselves.
 

jt20vt

Active Member
Sep 17, 2010
159
31
You have crankshaft position sensor fault which could be causing the cutting out of the engine and poss the erratic behaviour of the dsg gearbox. There are several YouTube videos of people having cars cutting out due to a fault with the crank sensor. The other faults might be a result of the car getting confused. As woody has said check the wheel speed sensors to rule them out.
 
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Woody_72

Active Member
May 10, 2020
497
245
Northwest England
That's a very good point. A lot of cars use the crankshaft position sensor to monitor engine speed (not %100 sure if SEATs do or not though, a few car brands use the camshaft position sensor) so if that value's erratic, it would explain the rest of the car getting confused.
 
Dec 13, 2021
3
2
Northern Ireland
That's a very good point. A lot of cars use the crankshaft position sensor to monitor engine speed (not %100 sure if SEATs do or not though, a few car brands use the camshaft position sensor) so if that value's erratic, it would explain the rest of the car getting confused.
You have crankshaft position sensor fault which could be causing the cutting out of the engine and poss the erratic behaviour of the dsg gearbox. There are several YouTube videos of people having cars cutting out due to a fault with the crank sensor. The other faults might be a result of the car getting confused. As woody has said check the wheel speed sensors to rule them out.
Thanks for the suggestions, I'll pass them on and see what comes of it :)
 
I would bet you have a dodgy rear wheel bearing and/or ABS sensor. I had very odd problems with my 1P Leon DSG that first manifested as a reluctance to change up in D, then it did a couple of jumps up and down the box, then lit up the dash with ESP and TPM errors but drove normally. It didn't store any codes until that final point.
 
Dec 13, 2021
3
2
Northern Ireland
Good eve to all that may stumble across this thread in the future or be receiving updates on it from when i last posted in it.

The issue as explained to me by the trusty mechanic was a combination of 4 things

1) The crankshaft position sensor itself had a load of metal shavings stuck to it.

2) One single wire going from the ECU to the crankshaft sensor connector was broken on the inside but cosmetically fine from the outside, making it pulse between -2V and +3V instead of between 0V and +5V(reference circuit B from my report)

3)The mechatronic unit was outputting crazy random wave functions when measured with an oscilloscope. So that was replaced

4)Mickey mouse set up a club house in my glovebox and was likely making trips to the back alley of dashboard town and chewing down on some tasty wires because he was definitely grand chewing on my tax certificates and emergency tissue stash.
 
DPM Performance