This might bore some, but I guarantee one or two people will find this interesting.
My car is now over 7 years old, and approaching 100k miles. That’s not the magic figure it used to be, but you have to accept a few things will fail- so, outside of the consumables, I’ve had a (surprisingly pricey) gear lever, a similarly pricey blower motor, a few suspension bushes, a dual-mass flywheel, and now, a sensor with a surprising symptom.
The surprising symptom was the DSG gearbox getting increasingly reluctant to change up when in D (full-auto) mode, back in October. No codes stored, and a manual change avoided it.
The fear at this point is a mechatronics failure- the unit is pricey, even refurbished, but that seems unlikely, given the change works manually, and a mechatronics failure is usally a bit more obvious.
Fortunately, someone had been here before, and I remembered his post on good old usenet, describing the symptoms, and dropped him an email. His answer:
I’ve got no fault codes but the symptoms sound a bit similar. In my case , the problem turned out to be a corroded sensor ring on one of the rear wheels.
Replacement wasn’t cheap though. It seems that wheel bearings etc also had to be replaced. Still, a lot cheaper than a gearbox repair.
For some reason the defective sensor input to the gearbox was screwing up it’s speed assessment but wasn’t triggering any warning lights.
Changing them isn’t cheap, as he said: a quality part is around £100, and the fault was very intermittent, so I left it, changing manually if needed. I had to wait until today- when the gearbox suddenly decided that 1st was appropriate at 15-20mph (1st being very, very low in DSG cars), got all confused, decided it wasn’t again, then; finally, lit up the ABS, stability control, and tyre pressure warning lamps, then drove normally. Code stored was:
Address 03: ABS Brakes Labels: 1K0-907-379-MK60-F.lbl
Part No SW: 1K0 907 379 AA HW: 1K0 907 379 AA
Component: ESP FRONT MK60 0102
Shop #: WSC 06441 785 00200
1 Fault Found:
00287 - ABS Wheel Speed Sensor; Rear Right (G44)
003 - Mechanical Failure
This is odd. ABS causes no upchange? Previous searching had thrown up this (read post number 4).
The gearbox, in collusion with the ABS and stability ECU, will refuse to change up if the speed signal from the rear wheels (which it gets over CANbus) seems odd, or confuses it into thinking you’re cornering (because you don’t want an unexpected upchange half way around a corner). Sane enough, I suppose, but very unexpected, and, of course, not going to show up on a manual car- it seems the gearbox starts getting confused way before the ABS controller decides the input is dodgy, so a manual car would drive normally until the dash lights appeared.
This oddity is going to be common to cars on the PQ35 platform- my correspondent above had a VW Touran:
Audi A3 Mk2 (8P)
Audi TT Mk2 (8J)
Volkswagen Touran (1T)
Volkswagen Caddy (2K)
SEAT Altea (5P)
Volkswagen Golf Mk5 / GTI / R32 / Rabbit Mk5 (1K)
Škoda Octavia Mk2 (1Z)
Volkswagen Golf Plus (5M)
SEAT Toledo Mk3 (5P)
Volkswagen Jetta Mk5 (1K)
SEAT León Mk2 (1P)
Volkswagen Tiguan (5N)
Volkswagen Scirocco (13)
Volkswagen Golf Mk6 (5K)
Škoda Yeti (5L)
Volkswagen Jetta Mk6 (1K), (16)
Audi Q3 (8U)
Volkswagen Beetle (16)
and maybe others, with a DSG gearbox and that design of rear hub (it seems the wheel bearing, sensor ring, and hub are one assembly).
It does say something (again) about the complex, networked nature of modernish cars. The concept of a sensor in the braking system affecting gearchange is a bit non-obvious, but when you have sensors there anyway, required for (legally mandatory) ABS, and a network to talk over, may as well use them, huh?