[Bush pig]

Hi, Thanks for replying.
I think a sensor problem is probably causing the ECU to stay in limp-home mode.
Sensors are wired to the ECU.
The ECU has been tested and no-fault-found.
Diagnostics simply say 'Comms error' for ECU module.
The upshot is I cannot find out what sensor is faulty.
Most modules have CAN and K-line.
The BCM (On Board Power Supply CU in VW-speak) has no K-line connection but has CAN to the Dash panel insert. It all tests OK.
I have the full VW current-flow diagram with what looks like every variant by month and model (2859 pages of pdf)!!
Relevant pages show a hard wire connection between the diagnostic socket and the ECU - grey/white wire.
I think DTCs will be reported via K-line.
Using Picoscope on a breakout for the diagnostic connector shows that queries for each module are sent via K-line.
The ECU doesn't respond.
Using a camera probe I can see a grey/white wire going into orange T10h/2. I cannot manage so far to get a meter probe down into it.
I've tried making a probe with a needle and a bit of stiff wire but the spaghetti of other wires makes positioning the camera and aiming the probe difficult.
It looks as if the connector tray is meant to slide upwards for access.
Maybe a previous owner had a go and the tangle of wires makes that look risky.
I don't want to use brute force.
I'll have another try when the weather improves.
It's a bad idea to try vehicle repairs in the open on the west coast of Scotland.
Cheers.

 

[Bush pig]

Thanks triffic,
I've now got hold of SSP311, pages 84/85 show the hardwired and virtual wire setup.
I'll also look at SSP186 and SSP238.
My model is very basic; manual windows, manual gearbox, simple steering wheel etc.
You could be right that I'm concentrating on K-line T16/7 >>> T94/72 and it isn't the problem ... but they should be connected.
So I will try to find why they aren't ... just so I can re install the battery etc.
I can then re-run VCDS and look at some waveforms.
Attached is a pic of the harness just before the E-box ... gives an idea of why I'm chasing this.

Solid rain forecast for next 2 days so it will have to wait.
Cheers.