A warning light is back

The news is, unfortunately, that car has again thrown up a warning light, although this time it is something new.

I was travelling along on a recent drive, when all of a sudden the airbag warning light came on. The performance and operation of the car wasn’t affected at all (apart from the big warning light on the dash, which I know all about anyway). I continued on and parked the car in the hope that it may reset after the engine had been turned off.

Unfortunately, taking the car out again proved that the airbag warning light needs more attention that simply turning the engine off. The car’s performance is no way affected but that red warning light on the dash is annoying.

As you can see from the above diagram the car has two airbags, driver and passenger. The ECU (item 1) that controls the airbag is located under the front console.

Reading the F355 workshop manual on airbag issues you see:

Being a safety system, the airbag individual components cannot be repaired. To detect the faulty component, use the SD-1 system and then replace it.

From what I tell you need to hook up the diagnostic (SD-1) to connector A shown above.

That connector in the passengers foot well along with the fuses as shown above. There seems to be a procedure in which you can short pin 1 of the diagnostics connector for 1 – 5 seconds and the following sequence will show on the air bag warning lamp on the dash, depending on the issue:

Lamp check : Fault

1: None (the lamp switches on for about 4 seconds, when ignition key is put in position”II”)

2: Faulty sensor

3: Airbag starting circuit short-circuited towards battery +

4: Airbag starting circuit short-circuited towards ground +

5: Wrong driver’s side airbag resistance

6: Wrong passenger’s side airbag resistance

7: Low battery voltage

8: Faulty light or circuits

9 Stored crash data

After the last fault, the first one is shown again.

The faults can be cancelled (apart from no. 9) by short circuiting the pin no. 1 of the diagnostics socket connector towards earth for a time between 5 and 10 seconds.

If the fault no 2. (ECU inner failure) disappears, the sensor resets.

So it looks like I could attempt to determine what the fault is and then attempt to reset this by simply grounding one of the connectors. However, I think the first thing I need to do is talk to someone a with more knowledge about these things before I try anything and see what they recommend. I really don’t want to be mucking about with the airbag system, without knowing what I’m doing, just in case I set it off or something. So I need to make a few calls before I go much further.

Now the ECU unit that controls the airbag is located under the console between the seats. I was wondering how you would get to it if you needed, and once again YouTube to the rescue with these videos: