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 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 B0078 can be set when the right SIS malfunctions. The following conditions
must be met to set this DTC:
| • | Ignition voltage is present at the SDM and continuous. |
| • | The SDM detects a right SIS fault. |
| • | The SDM resets the right SIS twice without detecting correct operation. |
Action Taken When the DTC Sets
| • | The air bag telltale will be on. |
Diagnostic Aids
| • | When attempting to diagnose an intermittent passenger loop
fault, use the scan tool to monitor the current DTCs. Wiggle the sires and check the
connections while watching for a current DTC to appear and/or disappear on the scan
tool. |
| • | Always start diagnosis of the SIR DTCs with an inspection of the vehicle,
including its wiring and the SIR components for visible damage. |
| • | A short to ground in circuits 2133 or 2134 could cause this DTC. |
| • | A short between circuits 2133 or 2134 and another vehicle circuit
could cause this DTC. |
B0078
