For 1990-2009 cars

The SIR Scan Tool Data Definitions contain a brief description of all SIR related parameters available on the scan tool. The list is in the order it appears on the scan tool.

Ignition: The scan tool displays 0-25.5 volts. The Ignition represents the system voltage measured by the SDM at its ignition feed.
Lamp Driver: The scan tool displays Internal or External. The warning lamp control method for a hard wired lamp is Internal. The warning lamp control method for a serial data controlled lamp is External.
Driver Resistance: The scan tool displays 0-6.3 ohms. The SDM performs the resistance measurement test once each ignition cycle and verifies the Ignition 1 and the 23 VLR voltages are within the normal ranges. Then the SDM sources a constant current to the driver deployment loop. The SDM then measures the voltage drop across the deployment loop and converts the measured voltage value to a driver deployment loop resistance value.
Passenger Resistance: The scan tool displays 0-6.3 ohms. The SDM performs the resistance measurement test once each ignition cycle and verifies the Ignition 1 and 23 VLR voltages are within the normal ranges. Then the SDM sources a constant current to the passenger deployment loop. The SDM then measures the voltage drop across the deployment loop and converts the measured voltage value to a passenger deployment loop resistance value.
Driver Senselo: The scan tool displays 0-20 volts. The SDM measures the voltage of the driver low terminal voltage and displays it as Driver Senselo.
Passenger Senselo: The scan tool displays 0-20 volts. The SDM measures the voltage of the passenger low terminal voltage and displays it as Passenger Senselo.
Driver VDIF: The scan tool displays 0-500 millivolts. The SDM measures the voltage difference between driver high and driver low and displays this voltage difference asDriver VDIF.
Passenger VDIF: The scan tool displays 0-500 millivolts. The SDM measures the voltage difference between passenger high and driver low and displays this voltage difference as Passenger VDIF.
Warning Lamp ON: The scan tool displays 0-182 hours. The SDM measures the continuous warning lamp on time.
Warning Lamp Cycles: The scan tool displays 0-125 cycles. The ignition cycles of the current warning lamp state.
Driver Seat Belt: The scan tool displays Buckled or Unbuckled. The signal from the drivers seat belt switch that the seat belt is fastened.