Fixing BMW parking sensors

A friend had a noticed that his parking-sensors where no longer working from his BMW 1

After he examined his OBD, he noticed that the parking-sensory board wasn’t working properly (read missing)

Probing the ODB

bmw-not-found

So he searched in the manuals for the parking module. And this is what he found when he accessed the trunk:

 

The trunk, accessing the parking modules
The trunk, accessing the parking modules

It probably should look like a small pool, should it?

mmm... a disturbing amount of water
mmm… a disturbing amount of water

Apparently, when changing the rear lights from this model, there is a rather large probability that when putting the whole thing back, you mess up some insulation. As a result, rain pours in when driving . Having placed the module in a small cabinet without drain, makes for a corroding environment.

The module, contained the main-board, responsible for detecting distance is looking not too great, after exposure to rain and current:

yes, that is mold what you are looking at
yes, that is mold what you are looking at
A combination of current and moist, has corroded the entire power-supply to the power-regulator
A combination of current and moist, has corroded the entire power-supply to the power-regulator

 

As my friend did enjoy having parking-sensors, he inquired into replacement modules.

2nd hand, they where a whopping  €150,-  so he didn’t bother looking into a brand-new part

The corroded part is an ST L49493p, which turns out to be a 5-volt low-drop regulator, with 100mA of regulating-power.

So after a quick search on Ebay, we found a new chip, it was rather expensive with €9,- but still, a laugh comparing to a new main-board.


So we replaced the part:

bmw-soldering-chip
prepping my soldering mate

bmw-parking-removing-old-chip

 

As the water and current had ruined a track underneath the chip, I had to make a bypass, in order to make the chip get power on it’s input pin, like a proper surgeon.

bypassing a lead, due to a corroded print-track
bypassing a lead, due to a corroded print-track

After putting the PCB back into the Bosch casing and reattaching the cables in the car, it beeped again 🙂

The diagnostics software reports all OK
The diagnostics software reports all OK

In retrospect, any 5-volt fixed regulator, capable of handling up to ~13 volt, and sourcing <=100mA  should have worked, so 7805… might have done the trick as well.