Disassembling BMW's airbag ECU: The layout and wiring are amazing

Recently, we received an antique airbag controller removed from a BMW by a netizen. The 03-08-14 on the label may be the production date. Was it produced on August 14, 2003? According to relevant information found on the Internet, this airbag control unit is also used in the Range Rover L322 (2002-2009) model, which is what we usually call the Range Rover. It seems that it has a wide range of applications.

The controller has 3 mounting holes for fixing to the car body, and 4 screws for fixing the cover. The cover has some striped patterns stamped on it, which may be used to increase the strength of the cover.

There is a huge detachable wiring harness on the top of the controller. There is a white connector removal/installation device on the wiring harness. When it is moved to the left, the yellow connector will detach from the controller, making it easy to remove the wire speed. When it is moved to the right, it will be compacted and locked.

The white disassembly/assembly device will be stuck by the yellow protrusion after being locked, which can prevent vibration from causing the white device to rotate to a position where it should not go.

This controller also has a very high amount of wires, with many pairs of wires twisted together, and only a few wires are single-wire dogs. I checked some information and learned that the airbag controller is used to detect sensor signals, and decide whether to energize the airbag's "detonator" based on the collected data. After detonation, the gas generator will inflate the airbag, and the airbag needs to be deflated after the impact.

The cover can be easily removed after removing four screws.

There is no waterproof treatment between the cover and the shell, but the PCB is coated with a large amount of three-proof paint, so the PCB is waterproof.

After removing the cover, you can easily remove the mainboard. The large number of PLCC-packaged chips on the mainboard expose the age of this controller. It is very likely that no information can be found for this type of chip.

Fortunately, this shell is made of cast aluminum, so it has some weight and is worth some money.

The contact parts of the connector pins are also gold-plated.

The connector on the other side is covered with the white disassembly device. There are two tooth-like protrusions at the bottom, which can push itself up and down. It is easy to remove the wiring harness through it. You should know that this multi-pin wire-to-board connector is very troublesome to disassemble. If you don't use enough force, it will not come off. If you use too much force, it will suddenly fall off and either bend the pins or hit the back of your hand. You may even get an electric shock on your chin.

There are two large capacitors on the motherboard, which looks like a small power amplifier. It is speculated that this pair of capacitors is to extend the life of the vehicle after the main power is cut off during a collision, so that the vehicle has enough strength to detonate the "detonator" in the airbag.

Both capacitors are 25V 3900uF. I can't tell what brand they are. The electrolytic capacitors have not bulged after so many years, so the quality must be very good.

There are three 30420 chips printed with Bosch LOGO on the back of the motherboard. I can't find any information about them, but judging from the wiring, they should be line driver or level conversion interface chips. There are small waves of conformal paint on the bottom left corner of the three chips. I'm curious, from which direction can the small waves of conformal paint be concentrated in the bottom left corner?

There is also a small wave of conformal paint on the chip on the front, especially the small wave on Motorola, which looks like half of the face is exposed.

Among these chips, only Motorola's chips look very thin, with tiny pins, densely packed and fashionable.

There are also two Bosch LOGO silk screens on the front, which indicates the 30420 chip.

The Bosch logo on the chip on the right looks like an axle with two wheels. I wonder if this is what Bosch considered when it was first founded. But if Bosch were a fitness brand, I might still think it looks like a dumbbell.

The connector housing can be easily removed by removing the white plastic on the side of the harness connector.

The terminals without the connector housing cover look just like ordinary KF2510-2.54 terminals.

Take out a pair of cold-pressed terminals, it looks very similar to the DuPont madman, but the DuPont terminals are all copper. This terminal is copper inside and covered with a metal sheet that should be stainless steel on the outside.

There is an identification area on the motherboard with a serial number and the Bosch logo. 20-03 should be the date code, the 20th week of 2003, which is close to August 14, 2003 on the label and earlier than the production date of the module.

The layout and wiring on the motherboard looks very comfortable, and the yellow copper sheet under the green oil reveals a retro style.

The crystal oscillator next to the Motorola chip reveals its leading position on this motherboard. The silk screen on the crystal oscillator looks like 4000HZ.

A 10020B chip of the German ELMOS brand, said to be an I-BUS driver, but I only heard about it and couldn't find any official information.

This 47uF tantalum capacitor from EPCOS (TDK) looks very beautiful.

Is this Bosch chip marked with an X a scrapped chip? If you look closely, it is X62, perhaps it is the QC PASSED mark of the inspector X62?

The motherboard uses some MELF packaged capacitors, which look very precise, but the tin on some of the pads does not seem to be very full.

The large amount of conformal coating remaining on the bottom of the chip makes the chip look appetizing as if it had been fried in oil. Although more than 20 years have passed, the smell of the conformal coating has not completely dissipated.

The connector on the motherboard is soldered using wave soldering. I heard that connectors soldered with tin are easy to fall off in such high vibration situations. Compared with the previous Press-fit, it is more reliable. However, this connector has also made great efforts in terms of reliability. There are two black plastic columns and two white plastic columns on the left. There are three rows of pin headers in the middle, and there is another row of pin headers on the right for grounding and fixing.

There is a rectangular device inside the white plastic column. It should be pressed down after the plastic is assembled to lock the plastic and PCB in place. The principle is somewhat similar to that of an expansion screw.

The copper used in the cable is quite abundant, and the gold plating in the cold-pressed terminal is also very yellow.

The white metal piece on the outside is more elastic and is used to snap into the hole in the yellow plastic.

The pin headers on the motherboard also seem very sturdy and look like new after all these years.

The workmanship of this airbag controller seems to be very good, and it can also be seen that the car installed with this controller should be well maintained. Both the inside and outside of the controller and the wiring harness look quite new.

Finally, here is a picture of a crystal oscillator. Can you guess why this crystal oscillator has 6 pins?

Do you like our articles? Welcome to follow our WeChat subscription account: Auto Development Circle (ID: AutoDevelopers) to browse more automotive electronics related content.