Hi. Having the following intermittent (everyone’s favourite) electrical problems:

1) Clock and trip mileage reset themselves; display switched itself from mileage-left-in-tank to outside temperature

2) Interior light doesn’t always come on when the driver’s door opened

3) Relocks itself, and alarm reactivates, despite drivers door being opened following door unlock

using fob

4) Boot no longer opens along with doors (used to)

I was thinking it may be the ECU degrading (I have a late 2007 Mark 2 1.6 petrol manual Fabia with 113000 miles) and have been investigating getting a replacement ECU (breakers) or having the ECU flashed. Anyone have any ideas before I proceed down that route? Thanks.

I have no idea which Electronic Control Unit you're referring to, but it (whichever) would be absolutely the last place I would look for a solution.  They tend to be far more reliable than the things with moving parts like microswitches and wiring looms between body and doors.

 

For 1, check cabin fuses first, a permanent 12V feed may not be getting to where it should if a fuse has blown.

 

Interior light oddities and relocking are both consistent with the door-open microswitch either not working, or its status not being conveyed to the relevant control unit because of broken wiring. Mk2 Fabias are infamous for the wiring near the A-pillar snapping  within the door bellows.  It's a poor design, low quality wire, or both.  Investigate this area first.

 

 

 

 

2 hours ago, Wino said:

I have no idea which Electronic Control Unit you're referring to, but it (whichever) would be absolutely the last place I would look for a solution.  They tend to be far more reliable than the things with moving parts like microswitches and wiring looms between body and doors.

 

For 1, check cabin fuses first, a permanent 12V feed may not be getting to where it should if a fuse has blown.

 

Interior light oddities and relocking are both consistent with the door-open microswitch either not working, or its status not being conveyed to the relevant control unit because of broken wiring. Mk2 Fabias are infamous for the wiring near the A-pillar snapping  within the door bellows.  It's a poor design, low quality wire, or both.  Investigate this area first.

 

 

 

 

Thanks Wino, have checked some fuses and none were blown. Good to know about ECU reliability. I have read about A pillar problems and was about to investigate the wiring and door lock mech when the display starting playing up. I then thought there may be a wider problem, maybe with the main brain, which I thought was the ECU under the bonnet (near firewall). But that based on very little knowledge, as I am sure is evident. I have also had problems with engine warning light showing but no fault codes being recorded and no obvious faults, and low oil warning light when oil near max and new sensor installed. All suggested a major breakdown in software. Anyway, you given me somewhere to start, thanks for your time and consideration.

No problem Dave, and welcome to Briskoda, by the way.

 

Your Fabia is fairly chock-a-block with control units and it's not really the case that the engine ECU is the main brain, just the main engine control. The interior light, door locking and even oil level monitoring are not within its scope of operation.  Oil level (and temperature) data are processed by the instrument cluster itself, which is a control unit in its own right.

If you're handy with a soldering iron, reflowing the solder joints of all the connector pins from the two connectors on the instrument cluster circuit board can solve a number of problems, especially where the misbehaviour is intermittent/inconsistent.

Here's an image showing the various 'brains' around your car. Clockwise from the top: ABS, Instruments, Central Convenience, Engine, Power Steering, Airbags and HVAC (heating +A/C).

 

In the middle, is the unit that arguably is in overall charge, referred to by a confusing array of different names, Onboard supply Control unit, Vehicle Voltage Control Unit, Body Control Module etc.  It is the hub of all communication and control activity, co-ordinating everything else. It is located above the accelerator pedal on RHD cars.

 

 

 

What has been used to try to read engine fault codes? To the best of my knowledge, if the warning light has been on, there will be codes stored, they just may not be readable by every device capable of connecting to the OBDII socket.  Try to find a local member or garage with VCDS, an aftermarket system that talks 'properly' to the VW-group systems; that should be able to find any and every stored fault code, in any of the above modules/ECUs.

 

If the door-related faults are happening every time, I'd say it might be a broken wire or two in the bellows, but if they are more unpredictable and sometimes work as expected, more likely the door-open microswitch on the lock module (or its wire solder joints onto the circuit board inside).

 

 

 

Edited 10 November, 20205 yr by Wino

" 1) Clock and trip mileage reset themselves; "

 

In previous cars I have owned, this can be the first indication that the battery is on the way out.

When the car is started the voltage drops low enough for these to reset themselves.

 

Check the battery voltage after the car has been standing for a day or two.

Should be 12.5v or above.

15 hours ago, Wino said:

Interior light oddities and relocking are both consistent with the door-open microswitch either not working, or its status not being conveyed to the relevant control unit because of broken wiring. Mk2 Fabias are infamous for the wiring near the A-pillar snapping  within the door bellows.  It's a poor design, low quality wire, or both.  Investigate this area first.

 

Not only Fabias & Roomsters, but also Yetis.  I'm on a Yeti-specific Forum where owners of early Yetis have reported all manner of seemingly unrelated faults caused by broken wires in the door bellows.  Not sure about Fabias but later Yetis used a modified wiring loom to overcome the problem. 

Edited 10 November, 20205 yr by Robjon

8 minutes ago, PipH said:

" 1) Clock and trip mileage reset themselves; "

 

In previous cars I have owned, this can be the first indication that the battery is on the way out.

When the car is started the voltage drops low enough for these to reset themselves.

 

Check the battery voltage after the car has been standing for a day or two.

Should be 12.5v or above.

 

Good point.

Any chance the car is still on its original factory-fitted battery? (Having a VW/Skoda part number on the top surface is often a clue to this, if you aren't the first owner and don't know.)

6 hours ago, Wino said:

No problem Dave, and welcome to Briskoda, by the way.

 

Your Fabia is fairly chock-a-block with control units and it's not really the case that the engine ECU is the main brain, just the main engine control. The interior light, door locking and even oil level monitoring are not within its scope of operation.  Oil level (and temperature) data are processed by the instrument cluster itself, which is a control unit in its own right.

If you're handy with a soldering iron, reflowing the solder joints of all the connector pins from the two connectors on the instrument cluster circuit board can solve a number of problems, especially where the misbehaviour is intermittent/inconsistent.

Here's an image showing the various 'brains' around your car. Clockwise from the top: ABS, Instruments, Central Convenience, Engine, Power Steering, Airbags and HVAC (heating +A/C).

 

In the middle, is the unit that arguably is in overall charge, referred to by a confusing array of different names, Onboard supply Control unit, Vehicle Voltage Control Unit, Body Control Module etc.  It is the hub of all communication and control activity, co-ordinating everything else. It is located above the accelerator pedal on RHD cars.

 

 

 

What has been used to try to read engine fault codes? To the best of my knowledge, if the warning light has been on, there will be codes stored, they just may not be readable by every device capable of connecting to the OBDII socket.  Try to find a local member or garage with VCDS, an aftermarket system that talks 'properly' to the VW-group systems; that should be able to find any and every stored fault code, in any of the above modules/ECUs.

 

If the door-related faults are happening every time, I'd say it might be a broken wire or two in the bellows, but if they are more unpredictable and sometimes work as expected, more likely the door-open microswitch on the lock module (or its wire solder joints onto the circuit board inside).

 

 

 

Again, many thanks for your time and expertise, it is greatly appreciated.

I will admit to experiencing signs (websites offering many ECU types) that not everything was dealt with by the ECU I referred to, I think there may have been a certain amount of "I hope I can just change that, get it programmed and happy days" going on in my head. It comes as no surprise that it not that easy ha ha.

I have been on Briskoda before, many years ago. Dunno why it says I am new, I have posted and received excellent assistance previously. Does highlight the fact that my Fabia has been amazingly reliable, I love it. I have had an Audi and a VW, and had far more problems with them (but then they were higher performance models and may have had a hard life).

I use a cable and software that I bought off eBay to access error codes. Obviously not the full VCDS, but think it offers more functions that the freeware version. Will let me access most modules individually to download codes. I am not 100% confident it is fully operational however. I may try reinstalling it. I do have a friend with a code reader device as well.

You have given me further avenues for investigation and ideas for rectification, I shall crack on with those. Car still works fine in the main, but would be nice to get the niggles sorted.

5 hours ago, PipH said:

" 1) Clock and trip mileage reset themselves; "

 

In previous cars I have owned, this can be the first indication that the battery is on the way out.

When the car is started the voltage drops low enough for these to reset themselves.

 

Check the battery voltage after the car has been standing for a day or two.

Should be 12.5v or above.

Ah, another excellent idea, thanks. Battery has never been changed and ambient temperatures now low, so that's one to check out

5 hours ago, Wino said:

 

Good point.

Any chance the car is still on its original factory-fitted battery? (Having a VW/Skoda part number on the top surface is often a clue to this, if you aren't the first owner and don't know.)

Pretty sure it got the original battery. I got the car at 36000 miles, was only a few years old, unlikey it been changed. Will have a look for that part number, got multimeter at the ready.

5 hours ago, Robjon said:

 

Not only Fabias & Roomsters, but also Yetis.  I'm on a Yeti-specific Forum where owners of early Yetis have reported all manner of seemingly unrelated faults caused by broken wires in the door bellows.  Not sure about Fabias but later Yetis used a modified wiring loom to overcome the problem. 

Thanks Robjon