Hi folks,

Trying to fix a 2004 Fabia 1.4 auto belonging to my boss's wife. There's a 150mA battery drain that has caused no-start problems twice in the last 3 months.

Traced today to mostly fuse 43, designated "Onboard power supply control unit, selector lever lock" in the wiring diagrams.

That fuse seems to feed (red dot below) two devices within the onboard ps control unit, one of which isn't fitted in the spare I have (manual car version I think) and from that unfitted chip, goes out (upward blue arrow) on connector pin 1 of T18b, heading for the "Selector lever lock magnet, N110" which I've never heard of, but I guess is a solenoid lock mechanism near the auto selector lever?

I guess the device (right-pointing blue arrow), omitted-component below that feeds that lock solenoid has failed?, or the solenoid itself? (but I can't see why that would be intentionally powered when the car's locked)? I'm tired and not thinking clearly about this.

 

 

 

 

Anyone had something like this happen?  I guess something non-normal must be occurring with the selector lock if it's taking power all the time? Unless the power isn't getting beyond that non-fitted device. Diagnostic tips anyone? What does the selector lock even do?

 

Is it no problem to extract the onboard power supply control unit and dig about in there? No re-coding or anything, PIN-codes or suchlike? Just whip off batt neg and take the thing out?

 

Ta for your thoughts and experiences.

Edited 3 September, 20169 yr by Wino

I think your on about the solenoid which basically physically stops you from putting the car in 'D' unless your foot is on the brake pedal?

Edited 30 March, 201610 yr by SuperbTWM

I imagine the lock makes it impossible to select reverse while the car is moving.

I think your on about the solenoid which basically physically stops you from putting the car in 'D' unless your foot is on the brake pedal?

Sounds probable, ta.  I'll ask her if that's happening, or if she can put it in D whenever. That should be a start.

I think your on about the solenoid which basically physically stops you from putting the car in 'D' unless your foot is on the brake pedal?

 

This sounds right. Perhaps the brake switch is faulty and the solenoid is permanently energised.

Sounds probable, ta.  I'll ask her if that's happening, or if she can put it in D whenever. That should be a start.

 

I only found this out recently (having never owned and Auto or had anything to do with them) when my Uncle couldn't put his old Galaxy into 'D' and that turned out to be the brake pedal switch not functioning correctly.

 

I presume modern cars have a more advanced way of locking the selector as when you press the brake it is a quite a loud mechanical clunk

Edited 30 March, 201610 yr by SuperbTWM

This sounds right. Perhaps the brake switch is faulty and the solenoid is permanently energised.

Interesting idea... And nice easy fix...

Couple of tests last night seem to have exonerated the selector lock solenoid.  I half-expected it to be possible to select D without pressing the brake pedal if the solenoid was energised 24/7; that didn't happen. I thought too, that taking fuse 43 in and out might result in audible clicking from the neighbourhood of the selector lever, but that didn't happen either, apparently.

 

Which takes me back to the main power feed into the J519 electronics (red-arrowed 5V regulator, above) being where the current is going.

 

I suppose I can check where that current is going by extracting one by one the connectors that go into J519? (Unless it's all being used within J519?)

 

Couple of google mentions of "Fabia fuse 43" talk about a TSB relating to a wiring problem somewhere in the cabin, anyone have any details of this?

I was looking at your picture and trying to understand the pinouts of the devices at the blue and red arrows respectively.

 

Can you confirm the voltages on the tabs of both devices.( also pin 3 )

For a voltage regulator you would expect it to be 0V or GND.

But for a FET it would be a voltage.

On my phone in a beer garden, but I can say that middle pin and tab of blue arrowed dude is terminal 30, permanent 12V (fused by no.43).
Can't tell on the other device, but it's a 5V low-dropout regulator.

I realised last night sometime that I'd made a schoolboy error, so this morning I looked at the other side of the board...
That same feed is the high side of a whole row of relay coils, one of which I suspect is spuriously being switched on for some reason.

 

Edit:

 

Here's a couple more pics, the (main) tracking of the 12V on the bottom of the board with relay coils ringed, red dot showing the incoming connection from Fuse 43, and the red arrow I think showing that the tab (opposite the square of 16 via holes) of the regulator on the topside does indeed appear to be 0V.

 

 

 

Here are the relays, some of them dual, on the topside.  Function labels are I think correct, but not 100% sure.

Edited 2 April, 201610 yr by Wino

A bit of progress, on this today. Re-measured the current drain with a meter in series with battery negative, this time fixed up so that I could close up the car fully and set the alarm, while still seeing the meter/reading.

Started off at about the same as before ~150mA, but when I went back an hour later it had dropped to 30-something mA (flicking between 29 and 37mA roughly).  So sometime in that hour something has shut down, but it doesn't go as low I would expect (my Polo flicks between 16 and 21mA or somewhere in that territory).  Gonna compare with the missus's Fabia when I get a chance, but that has no alarm, and isn't an auto, so not a very fair comparison.

 

Edit: Was just thinking about the flicking current values and realised it's probably due to the door-pin LEDs. 

 

 

I got very confused last evening, looking at wiring diagrams and the unit pictured above, and some diagrams from one of the SSP documents I have, not helped by the fact that the pictured unit came from ebay and I have no idea whether it came from a VW, Skoda or Seat. Despite the reg number being on the outer casing, couldn't find out presumably because it's a scrapped car; MOT and tax status look-ups didn't help me. The reason I wanted to know is that the fusing arrangement is different between Polo and Fabia, the equivalent pin on the Polo BCM has a 5A fuse feeding it, not the 20A fuse that is No.43 on the Fabia. :think:

 

Anyone got a dead unit from a Fabia they want to flog to me (for not much!)? :sun:

Edited 6 April, 201610 yr by Wino