Circuit Description
When the ignition is turned on, the SDM performs a self-test to diagnose malfunctions
inside the module. The SDM provides the input power to the SIS. When input power
is first detected, the SIS responds by performing the internal diagnostics. Next
the SIS sends and 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 and 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 the 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 SIR components for visible damage. |
B0079
