Circuit Description
When the ignition is turned on, the SDM performs a self-test to diagnose malfunctions
inside the module. The SDM provides input power to the SIS. When the input power is
first detected, the SIS responds by performing internal diagnostics. Next the SIS
sends an ID message to the SDM. The SDM will consider this to be a valid ID if the
response time is less than 5 seconds after the SIS is powered up. The SIS will
continually communicate a status message to the SDM. The SDM can reset the SIS by
removing and applying power to it.
Conditions for Setting the DTC
DTC B0079 can be set when an incorrect left SIS is installed. The following
conditions must be met to set this DTC:
| • | Ignition voltage is present at the SDM and continuous. |
| • | The SDM has received an ID message from the left SIS that does not match
the ID stored in the SDM memory. |
| • | The SDM resets the left SIS twice without detecting correct operation. |
Action Taken When the DTC Sets
| • | The air bag telltale will be on. |
Diagnostic Aids
| • | Always start diagnosis of the SIR DTCs with an inspection of the vehicle,
including its wiring and the SIR components for visible damage. |
B0079
