Im trying to fault find issues on my little 2001 polo gti.

I had a few error codes pointing at shorts/open circuits in the evap purge valve (I assume this means charcoal cannister) and the camshaft timing adjuster.

I have run the systems test for the evap cannister and I am not getting 12v... my multimeter swings from 0 to around 4v cyclically.. is this normal?

The charcoal canister and pipe work takes the vapours from your petrol tank back into the engine. In certain cycles or the ECU it opens the valve to burn off the petrol stored in the canister. I have one in the wiring for my Puma/Sylva ECU reuse application. I obviously don't have a charcoal canister (rather a big ugly thing). Even connecting the valve as a dummy load to the ECU does not remove the error code. I guess there must be more to the valve/ECU than I appreciate. The car runs fine no emission issues. Ignore the error code unless you are particularly green.

Hmm, its the fact that the error seems to be linked to the valve timing system... its a 16v VVt engine which presently doesnt seem to be dropping the cam at 4000RPm... hmmmm

I think you may have another issue, the cam has a position sensor that feeds back to the ecu. Much more likely I think.

I had considered that but I am not getting any errors from the cam sensor.

Have also discovered a blown fuse...which blows again when i replace it

Fuses primary purpose is to protect the wiring loom going on fire. If you have a fuse blowing then this has to be high priority regardless of engine performance. What is it's designation by VW?

Its a generic engine electronics system on a 5A fuse.

Trying to find a wiring diagram but so far no luck.

Error codes are as follows

17935 - Camshaft Timing Adj. Bank1 (N205): Short to Ground
P1527 - 35-00 - -
17911 - Load Signal from Alternator Term. DF: Implausible Signal (I think this one is caused by an aftermarket alternator with a shite recitfier on it)
P1503 - 35-00 - -
17833 - EVAP Purge Valve (N80): Short to Ground
P1425 - 35-00 - -

If I unplug either one, other or both of the items (timing adjuster or purge valve) I get "Open circuit" instead of "short to ground"

[Edited on 9/2/15 by tegwin]

The VVT and the idle control valves/solinoid (if they are like mine) are servo control actuators. They have a magnetic coil inside. The devices are pulse width driven from the ECU (a bit like a radio controlled model receiver output). Increases in pulse width changes the valve position in a very precise manner. You need to get hold of an oscilloscope to fault find these.

Key question: If you remove the VVT valve and or the idle control valve (the engine should run without them connected) does the fuse still blow?

I think your +12v feed to the actuator and the purge valve are shared from the fuse that keep blowing.
It sounds like you have a pinched wire in the loom, causing a short to earth.
What is your engine code?
I may have a wiring diagram, i can try to screenshot it for you.

Dave

That was my thought as well, I have repaired a couple of bits of loom in the past (doors and O2 sensors)
Its an AVY engine. 1.6 16v Polo GTI

I can only find ajv wiring diagrams, they do not appear to have vvt fitted.
The purge valve goes to fuse 3, 7.5a on there.
I will check on autoworks, there may be a diagram there, also a lupo gti should be the same.

Dave

Yes, lupo is more likeley... They only fitted the AVY engine to the GTI...and only really made a handful of those...

Description

Unfortunately no fuse numbers on the diagram or wire colours, but they definately share a fuse by the diagram.

The fuse guide shows purge valve on fuse 30 with egr, but vvt solenoid on fuse 1, i think the fuse guide may be wrong as i dont see egr on the wiring diagram.

Dave

Numpty question - have you examined the loom to check it's not damaged anywhere?

Had similar error codes on my dad's Rover 75 injection system; turned out a mechanic hadn't routed the loom properly during a service and it had chafed through the insulation and the injector was permanently grounded which mean a continuous fuel flow...