Replaced Water Pump,
Join Date: Aug 2009
Location: New Zealand
I've just solved all my airbag problems using FiatECUScan (although KWP71 from Sander works well too) and have learnt a few thing about Alfa Airbags. So here goes.
The early TRW airbag ECUs used an oddball timing on the comm protocol (which apparently is based on an early KWP version) so are generally impossible to read and clear without using Examiner. You just don't have the ability of select the correct baud rates, etc, to connect in the Windows environment.
Later model ECUs (check ePer for the more recent part numbers for the units that superceed the older parts) are very easily connected to via Pin 3 on the OBD connector. Either buy a cable from Rarebear or solder in a selector switch between pin 3 and 7 on the OBD connector like I did.
If you can open comms with the airbag but can't talk to it, you most likely have an older ECU and will have to go to a stealer/specialist to reset the light. Or you can do what I did and replace the current Airbag ECU with one you can talk to.
Earlier Airbag ECUs will not self-clear error codes once the error is fixed and require error codes to be cleared manually. Newer air bag ECUs will apparently turn off the airbag light after a few starts once the fault is fixed. But I've never actually seen this so can't confirm.
All error codes are a clearable apart from 01 which is fatal. These 'locked ECUs' can be repaired, but this seems to involve desoldering the surface mount CPU chip (a Motorola CMC68HC908**** in the case of the TRW airbag ECUs) reflasing and resoldering it back in. This requires a services of a specialist Airbag ECU repairer. There might be a way or reflashing via the chip via the OBD port to reset the 01 error, but I havent found it. An 01 error will cause the airbag light to stay on from the moment the key is turned on. Not go off then on again.
A lit airbag warning light doesn't stop the airbag sytem from being operational in every case (this is information from the Alfa DTE manuals) but how you can tell whether the error you have has shut down the airbag system or not, isn't obvious. So assume your SRS system isn't working if the light is lit.
Passenger seat sensors are expensive to replace, but why would you? The seat sensor is more trouble than its worth. The apparent thinking from Alfa for the seat sensor was 'why deploy the passenger airbag if the the seat was sans passenger?' The counter-argument is of course if you smash your car hard enough to deploy the air bags, an extra airbag going off is probably the least of your problems. It seems that this latter argument eventually won out, as the seat sensor was deleted out in later models and a dummy resistor fitted instead. This part is 60669119. Which you apparently can purchase. A cheaper way is cut the wires between the seat and the connector and to solder a 2K7 resistor to the wires thus removing the seat sensor from the circuit. As far as the ECU is concerned, as the dummy resistor is always there, there is always a passenger onboard. I have done this, it cost me 50 cents and it works.
So, if you want to turn off the airbag light you need to have an Airbag ECU you can talk to, the software to talk to it on a laptop, a serial USB to OBD cable that allows you access to the Airbag ECU K-line (which is Pin 3 on the OBD connector). Connect with the software, read the fault code, and then fix the fault, or else the light will just come back on. Clear the fault codes and your done.
Darryl in New Zealand
Last edited by KiwiAlfa156; 27-03-11 at 23:45.