HOW TO ACCESS CODES

A scan tool is needed to access all GM SRS codes. For the most part, most aftermarket scan tools can access GM SRS codes, such as SnapOn and OTC. It may also be possible to employ certain aftermarket SRS scan tools, such as OTC to perform the proper data-stream diagnostics. On late model GM vehicles, it may be necessary to synchronize the SRS or SDM module to the body control module.  This is always needed on a late model GM whenever an SRS or an SDM module replacement has been performed.  The procedure is to simply go to the BODY module within the Tech 2 scan tool or equivalent and performed a new SRS to body module synchronization. In the event that a Tech 2 is not available a code 1001 is always going to be present. This means that an SRS to Body module synchronization has to be performed. 

A second aspect of code extraction using the scan tool is to use an airbag sensor simulator to perform the diagnostics.  An airbag simulator is nothing more then a special resistor which is placed or connected right where the airbag goes.  This resistor, for all practical purposes, acts as the actual airbag.  In other words the SDM module will see this resistor and assume it for the actual airbag.  When this is done and the codes are erased, the SDM or SRS module will look for the proper resistance at this circuit.  If the code is gone and not reset again, the fault is with the airbag. Each airbag module has a specific resistance depending on the manufacturer.  Look elsewhere within this program for specific resistances depending on the manufacturer or vehicle that you're working on.  Remember that these resistors are matched to the actual vehicle that you're working on. A 2.0 Ohm value simulator is the norm, but there are variations between manufacturers. 

An airbag simulator tool can be purchased from different tool vendors.  These simulators tools actually make for a very fast and accurate SRS diagnostics.  As said before, by simply erasing the codes, substituting the suspect airbag module and re-scanning for codes you can assume the viability of the repair.  If the code doesn't pop up again then you know where the problem lies.  If on the other hand, the code is set in memory again, then the problem is in this circuitry or the wiring.  Do not probe on the airbag module with a digital multimeter or test light.  This may explode the airbag causing damage to yourself. As a final point, all airbag circuits tend to have higher than normal resistive values as the vehicle ages. So that a MATCHED airbag simulator may not work properly, due to increased resistance that may not pose a problem to the airbag deployment function. If this happens and the resistance values are very close to normal, change the simulator's resistance over or under 0.50 Ohms. This will compensate for a skewed resistive value without replacing other components that may otherwise raise the repair invoice.