Caddy 2012 1.6tdi - Wonts Start (Dash, ignition, and some other things all dead)

[aliS]

Evening All,

I have a 2012 caddy that is dead to the world. With no prior warning and after sittign for 5 days I went to start it in the morning and after turning over the engine for 1/2-1second every thing went dead. I recycled the ignition and it started without issue. I then drove 12miles to work and the dash would flicker on and off ever so often for about 1 second with no apparant loss of power or headlights but the instrument cluster would go on and off (no fading just on and off). Driving back from work no issues until 7 miles when everything cut out at 70mph and on second or thrid attemot restarted (after about 10 seconds) - I think the engine was still running but I couldnt be sure. I then parked up at a friends house near buy and checked the fuses and relays for anything obvious. Attempting to recommence driving and then the dash would light up like an iginition sequence following 1-2 second loss of power whilst driving away so I turned round and parked the van up.

I suspected an ignition switch failure due to the lighting sequence and thought I'd just try changing that - two days later I've changed the ignition and nothing. The symptoms I have are as follows:
- no dash lights at all (no odo or background light)
- no reponse from any ignition switch - voltage at ignition switch 0.9v
- side lights will work as will internal but nothing else
- No hazard lights
- radio ok,
- electric windows wont work of switches, will come down on the key fob but will not go back up, key in the lock will put windows up and down
- battery + to body earth 12.45v
- each positive of fuse box in engine bay to body earth 12.45v
- relays 100 under bonnet switched out for known good relay with no effect
- relays 646 and 645's rotated round positions to no effect
- relay 644 changed out for known good relay with no effect

This is as far as I've got as the van is abandoned at a friends, I don't have a code reader and just now I have no money to get it into a garage for someone to have a look at (I've just started a new job after several months off work so am strapped for cash). My gut instinct is that whatever provides power to the above circuits that are dead to the world has failed/parted or shorted out - would anyone suggest where to look?

Does this sound familiar to anyone?

Thanks in advance,

Ali

[aliS]

Hi again,

I’ve managed to get a code reader onto the car but it will not communicate (possible as I can’t turn the ignition). I’ve checked the ECU & BCM for obvious damage and loose wires to no avail.

I’ve routed around with a multi meter but starting to loose the plot with this.

Any ideas how I can read the codes? Will a particular type of reader be able to interrogate and ecu that is not powered.

Circuit boards in cam bus and BCM look ok.

[VAG-Abound]

Code reader should work witb ignition in ACC position, so no need to start engine. Jump leads from other running vehicle?

[VAG-Abound]

Ah, I see the problem. I think I'd pull radio and bring 12V from battery to perm and switched lead via fuse carrier from *********, spade terminals to loose fuse, etc. Or a spare terminal on the supply side og the fuse rack. Hopefully that'll get juice to control units.

[aliS]

I had wanted to do that but was concerned I might fry something...

[VAG-Abound]

That's why I'd put a fuse in the feed from battery. To check in advance for obvious problem check resistance from wherever you want to connect 12V to ground. Should be noticeably non-zero.

[aliS]

That's why I'd put a fuse in the feed from battery. To check in advance for obvious problem check resistance from wherever you want to connect 12V to ground. Should be noticeably non-zero.

Piggy backed a fused power feed out of the cigarette lighter to the ignition, managed to get the OBD II scanner to interact but no stored or pending codes found. P026 came up when the ignition was on but I think that was more to do with only having half the system to life. Couldn't start the car of the piggy back when introducing the last cable of the ignition sequence to the power source.

I had 644 and one of the three 645 relays function hotwiring the ignition but no function from the other two 645 or the 464/646 relays beside the steering wheel column. Dash lights never came on and only the blower seems to come to life.

Would the ECU and BCM always throw a code up?

My gut instinct is still water having shorted out something but still cant see anything for the love of me.

the voltage supply to the ignition is <1.0v and the 3 switches off which the single supply functions

hat have low impedance.

Any ideas where to start next?

[aliS]

As a quick update after suspecting the instrument cluster could possibly be the culprit I checked the connector to the cluster which was completely dead with perm live reading only 0.1v and the other two switches supplies reading 0L.

So my problem is between the + batt to ignition. Will trace the cables back this weekend

[Crasher]

You need to find out if it is the code reader or the car, that will show you where to start.

[aliS]

Thanks Crasher, a friend who works for a local vag specialist tried to read the codes to no avail also. After 5-6 weeks having forgotten about the van due to work and family commitments I spent a bit of time today checking out the ecu and connections and also the fuse box under the bonnet for the obvious - all connections where live Barr the fuses supplied from 100 fuel pump relay.

Will keep digging tomorrow -