Golf mk5 Gti - Total electrical shutdown

[bobbuild]

Arrived home from shopping, turned car off and went to open boot which was still locked. Pressed unlock on key fob, no response. Went back into car and tried unlock on door, no response and then tried to turn on ignition. Completely dead, no dash lights at all. Tried again a few minutes later and it came back to life, clock had reset to 0:0 and radio had lost presets. Almost as though battery had been disconnected but terminals are fine and battery is almost new. Anyone got any ideas what could have caused this? Bit concerned it may happen again in a less convenient location!!

[anonymous-user]

Have you checked the alternator side? Sounds like it's been running off the battery only and not been receiving a charge.

[bobbuild]

Don’t think it’s that. Nipped down to my local mechanic and everything appears to be ok. There were 3 error codes which all cleared ok. If I remember correctly, 1 related to a cooling fan issue which apparently is quite common, 1 did mention low voltage and the 3rd was an emission valve I think.

[anonymous-user]

Are the terminals 100% tight at both ends? Positive and negative side.

[bobbuild]

Absolutely. I think it is some sort of ECU glitch. Just wondered if anyone had experienced anything similar and managed to diagnose it.

[anonymous-user]

Used to be issues with the fuel controller which would run the pump ( drain the battery ) even when switched off.

[bobbuild]

The battery is absolutely fine. The symptoms were just like the battery being disconnected and then reconnected a few minutes later that’s why I think it may be an ECU issue.

[anonymous-user]

bobbuild said:

The battery is absolutely fine. The symptoms were just like the battery being disconnected and then reconnected a few minutes later that’s why I think it may be an ECU issue.

Could be. Obvious thought is a bad earth. More so with you saying a new battery.

[thegreatdogwood]

bobbuild said:

The battery is absolutely fine. The symptoms were just like the battery being disconnected and then reconnected a few minutes later that’s why I think it may be an ECU issue.

Makes sense to me too. If the car thinks the battery voltage is dropping too low then it goes into a kind of preservation mode where it switches off everything to try to save the remaining charge. The fact that the clock zeroed out is one illustration.

You mentioned it threw a voltage error code, so if the battery is fine then I'd agree ion checking for an ECU glitch or a bad earth.

[bobbuild]

I’ll have another look at the earth tomorrow but it looked ok on first examination. Knowing my luck it will be ECU, sounds expensive!