Mines doing this!
Sometimes it starts, and others it won't?
I try to start it... no luck, go back 20 minutes later, starts and runs fine. Park up go shopping, come back starts, drive somewhere else, another shop or something, go back and won't start.
It's such a pain.
Could this be the crank sensor?
Did you solve this mate?
And when you said doesnt start does it not crank or it does very slowly then stops?
As thats whats happening to mine
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Sometimes a crank position sensor might fail in a way that won't show up in any stored ECU faults that VAG-COM can read.
I'll have to look it up to be sure, but I believe the CPS is a variable-reluctance type sensor with an internal ferrite core and a coil around it. If the coil breaks continuity or shorts out or something, the ECU would see that as a fault. But if for some reason the ferrite cracked or managed to shift position, the CPS could lose its ability to read the teeth on the crankshaft and yet because it wouldn't be an electrical failure, the ECU wouldn't detect it as a fault.
So I've managed to do a diagnostic test. Here are the results:
Chassis Type: 1J - VW Golf/Bora IV
Scan: 01 02 03 08 15 16 17 19 22 29 35 36 37 39 46 47 55 56 57 75
76
Mileage: 183450km/113990miles
-------------------------------------------------------------------------------
--------Address 01: Engine Labels: 06A-906-032-AUM.lbl
Part No: 06A 906 032 AR
Component: 1.8L R4/5VT G 0007
Coding: 05500
Shop #: WSC 00000
VCID: 6ED9E25C2A82C968C27
2 Faults Found:
16706 - Engine Speed Sensor (G28)
P0322 - 35-10 - No Signal - Intermittent
17978 - Engine Start Blocked by Immobilizer
P1570 - 35-10 - - Intermittent
Readiness: 0000 0000
--------Address 15: Airbags Labels: 6Q0-909-605-VW5.lbl
Part No: 6Q0 909 605 A
Component: 0F AIRBAG VW5 01 0004
Coding: 12358
Shop #: WSC 01317
VCID: 356B0D300F54BAB0C3D
1 Fault Found:
01218 - Side Airbag Igniter; Passenger Side (N200)
32-10 - Resistance too High - Intermittent
---------Address 17: Instruments Labels: 1J0-920-xx5-17.lbl
Part No: 1J0 920 925 A
Component: KOMBI+WEGFAHRS. BOO V01
Coding: 05412
Shop #: WSC 00000
VCID: 2757D778C5F8D820411
Subsystem 1 - Part No: Ident
Component: Nr. WEGFAHRS.:VWZ6Z0Y2084584
Ident.-Nr. WEGFAHRS.:VWZ6Z0Y2084584
1 Fault Found:
01176 - Key
07-10 - Signal too Low - Intermittent
For the engine speed sensor fault, I assume it refers to the crank sensor? Would that also be the cause of the engine not starting because of being blocked by the immobiliser?