DTC 26 - Driver Initiator Circuit Open

Every time ignition switch is turned to ON position, SDM performs a series of self tests to check for internal malfunctions. If no internal faults are detected, SDM measures voltages in ignition 1, 36 VLR (back-up power supply), and deployment loop circuits. If all of these circuit voltages are within pre-defined parameters, SDM will measure resistance of driver-side inflator module. This is accomplished by allowing a small amount of current to flow from A1 terminal, through passenger-side inflator module and back to SDM via A2 terminal. voltage drop between two terminals is used to calculate resistance of inflator module. After this calculation is complete, SDM removes ground signal from A2 terminal and measures voltage at A1 and A2 terminals. If an open circuit is detected (resistance above a specified limit), SDM will set DTC 26. If this fault is occurring intermittently, most probable causes are damaged SIR wiring harness or a poor connection at driver-side inflator module, SIR coil, or SDM.

1. Discriminates between a faulty driver-side inflator module and a faulty SIR wiring harness.
2. Checks continuity of Green/Red wire between SDM terminal A1 and driver-side inflator module terminal D3.
3. Checks continuity of Green wire between SDM terminal A2 and passenger-side inflator module terminal D4.
4. Discriminates between a faulty driver-side inflator module and a faulty SIR coil assembly.

Fig 1: DTC 26 - Driver Initiator Circuit Open

Courtesy of GENERAL MOTORS CORP.