Mk5 GTI starts and then dies immediately

[PaulZR]

Hello all

Sorry to make my first post a request for help rather than something more positive...

My Mk5 - 83k miles, manual, black - has been pretty well behaved for the first few months of ownership, but it failed to start earlier this week and I am struggling to figure out why.

I've taken a short video to illustrate the problem but in short, the car appears to fire up but then dies immediately.

I initially suspected fuel pump so went to plug in VCDS, which I have used numerous times without issue. However, this time round I was given a  'Function not supported by the gateway' message. On further investigation with a multimeter (and some chat with Ross Tech), it looks like the CAN gateway is either not connected or not powered.

In addition and as you'll see at the end of the video, I'm getting traction and ABS warning lights plus three beeps and a flashing red warning exclamation point on the dash.

The battery is nearly new and fully charged, the tank is at least 25% full.

The fuel pump in the tank is getting 12v ok and I can hear a noise from it (albeit faint) when I turn the key, so I think that may be a red herring. Plus, I don't imagine the car would start at all if no fuel was getting to the engine.

So at this point I'm stumped. Can anyone suggest anything else I might try?

Thanks in advance.

[GreigC]

Strange issue. Like the clocks are not communicating to the ecu and shutting the car off. Ideally you need to read the codes from VCDS. Do you have another key? Try starting the car with that.

[PaulZR]

Ha, well spotted. I hadn't noticed that the dials weren't moving. That's weird.

I do have two keys but the problem is the same with either, unfortunately.

Did a bit of Googling including on the non-moving dials as a symptom and found a video where a similar problem on a Mk6 diesel was cured with a new can bus gateway. As they're fairly cheap and I will need a new one for the planned RCD330 upgrade anyway, I'm going to try swapping that out to see if it cures the problem.

[DBXdarkangel]

My old audi a3 did that. Turned out it was the emobilizer locking in due to the connector not in properly on the back of the clocks.

[PaulZR]

Popped the existing can bus gateway out this morning and it looks like I might have found the culprit:



Not sure how that connector has become so badly corroded. I'm a little concerned about the large red plug that goes into this unit, as it also appears to have suffered with corrosion. Will attach the new unit when arrives and see what happens.

[PaulZR]

Update to close this one off.

I acquired and fitted a replacement unit (7N0 907 530 N from a Seat Leon). Changed the coding at Address 19 to 350003, tweaked a couple of other things, car now runs fine.