What have I Fried??
 

Hi all,

Well the new amplifier arrived today, I plugged it in to test it before fitting and it was working well, so I set about installing it.

During the installation I had a battery charger on keeping the battery topped up whilst the doors were open.

As I was bolting the divider/mounting plate back into position I inadvertently let the metal ratchet handle touch the live wire coming into the fuse box, this created a short between the fuse box live and the car bodywork (see attached photo). There were sparks and scorching on the bolt that the ratchet was attached to.

I finished bolting everything up and turned on the ignition and the MMI has stopped working and I have gained a 'parking brake malfunction' on the DIS display.

I ran a VCDS scan and got the following faults for the parking brake, I have cleared them but they come straight back:

Tuesday,18,July,2017,15:56:03:32225
VCDS Version: Release 17.1.3 (x64) Running on Windows 10 x64
www.Ross-Tech.com

Address 53: Parking Brake Labels: 4E0-910-801.clb
Control Module Part Number: 4E0 910 801 A HW: 4E0 907 801
Component and/or Version: EPB AV1C1010 H01 1010
Software Coding: 0000221
Work Shop Code: WSC 00443 210 90890
VCID: 1D64D0C261B610FF26F-8048
3 Faults Found:

00576 - Terminal 15
012 - Electrical Fault in Circuit - MIL ON
Freeze Frame:
Fault Status: 11101100
Fault Priority: 4
Fault Frequency: 1
Reset counter: 141
Mileage: 239112 km
Time Indication: 0
Date: 2017.07.18
Time: 15:50:06

Freeze Frame:
Voltage: 11.70 V
Count: 41

02434 - Supply Voltage for Control Module for Left Channel
009 - Open or Short to Ground - MIL ON
Freeze Frame:
Fault Status: 11111001
Fault Priority: 2
Fault Frequency: 1
Reset counter: 141
Time Indication: 0

Freeze Frame:
Voltage: 12.21 V
Count: 112

02435 - Supply Voltage for Control Module for Right Channel
009 - Open or Short to Ground - MIL ON
Freeze Frame:
Fault Status: 11111001
Fault Priority: 2
Fault Frequency: 1
Reset counter: 141
Time Indication: 0

Freeze Frame:
Voltage: 12.32 V
Count: 113




VCDS can't make contact with any of the MMI system components.

I have checked all the fuses but they all seem good.

Any ideas chaps?

Thanks
Dave

Oh ****! What bad luck.

Regarding the EPB, have you checked the fuses above the battery?
Fuse 8 - Control unit for electromechanical parking brake -J540-, left parking brake motor -V282-, 30 A
Fuse 9 - Control unit for electromechanical parking brake -J540-, right parking brake motor -V283-, 30 A

Regarding the MMI, is the supply cable that touched the body still live?

I know, what a plonker!

The fuses are fine.

Regarding power to the MMI fuse box, I'm a novice with a multimeter , I've
Put it on the continuity setting and put the black lead on the battery negative terminal and then touching the fuse box live red wire with the red lead and there doesn't appear to be any continuity. Is that a correct test?

Thanks

From neutral on battery to power wire you should be a voltage setting. Continuity is for checking one end of a circuit to the other end to see if there is continuity ( no breaks in the wire )

To try and clarify that.
If you have a bulb or a fuse in your hand you would use "continuity" to check if they were good or bad. Open circuit or very high resistance would mean no continuity therefore blown bulb or fuse. Do not use continuity on live circuits.
What you need to use in your case is "voltage". Set the multimeter to 12 volts (probably 20 volt or 30 volt scale), connect the black lead to the vehicle chassis (most bolts would be at earth potential), then proceed to touch the red lead to various points in your circuit. Hopefully you will read nominal 12 volts at good points and zero at bad.
If checking a complicated circuit it is always best to make your first check in the middle. If the reading is good then the fault is in the final half, if reading is bad then the fault lies in the first half. This tells you which direction to make your second check, splitting the suspect area in half each time. This is mathematically the quickest way to find the problem.

I know, all boring stuff. Good luck with it. A short should only blow a fuse or cause a circuit breaker to open, it should not "fry" anything. Of course if the short was inside a module then anything could happen but in your case all you did was short the fusebox supply to earth so major supply fuse blown instead of minor circuit fuse. Any other symptoms should be circumstantial.
But then I'm only a boring old fahrt so what do I know????

Thanks for setting me straight on how to check the voltage correctly.

Ray,

Thanks for such a good explanation, it was that which led me to look for a mainline fuse. I traced the power wire from the MMI fuse box back to the battery output side where I discovered a 60A bar type fuse that I didn't know existed. It has blown, see attached photo. So hopefully I'll find one of those at a local garage and see if that restores the system.

Regarding the park brake fault, I haven't driven the car yet but I applied the park brake a few times and the message on the DIS has disappeared. I'll hook up VCDS tomorrow and see if it'll let me clear the fault codes.

Thanks again for your time Gents,will post back once I've done the work and let you know the outcome.

As ray says, a supply short shouldn't fry any of the electronics that feed from it, so I doubt you've damaged any ECUs.

The arcing and associated power fluctuations may have freaked something out though, creating a condition known as brownout that can leave some microprocessor circuits in a hung/crashed state.

I would try disconnecting the battery for a while first.


EDIT: Just seen your post above about the blown fuse. Hopefully that fixes everything!

Have you checked all the fuses up above the battery behind the lift up flap? I did something similar one day and blew the supply to the media rack on the port side.

Glad to help. I did not want to be overbearing or seeming to be a smart arse.I've had a year or three experience in the electrics/electronic fields and try to make things simple for folk that don't know their amps from their volts. :D
Really happy that you found the blown fuse. Replacing that will most likely sort most of your problems.

Mark is correct about brownouts, they can be a bugger, but usually these things on vehicles are inherrently pretty robust. Not always but it would not pay a vehicle manufacturer not to build in safeguards in the electronics area. After all a short either by a mechanic (like yours) or a case of worn insulation due to vibration is a common occurence.
I'll admit I nearly burnt a finger off in my younger days by shorting a 24 volt battery with my wedding ring. Lesson painfully and very quickly learnt.

Update:

Fuse installed and system restored, the replacement amplifier works a treat.

New batttery installed and coded. faults cleared in VCDS,new scan reveals a significant improvement in number of fault codes. I will post them in my other thread in this forum section for continuity.

Thanks a lot guys for your advice.