Action Taken

DERM turns on INFLATABLE RESTRAINT indicator light.

NOTE: Test numbers refer to test numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS .

Checks if fault is in steering column. SIR load tester simulates resistance of good steering column wiring and components.
Determines if fault is in inflator module or SIR coil. SIR load tester simulates resistance of a good inflator module.
Checks if 100-ohm resistor in resistor module is shorted.
Checks resistor module for internal shorts.
Checks resistance of circuits between resistor module and DERM.
Checks for SENSE HI shorted to voltage.

Fig 1: Code 21, Steering Column Resistance Too High

Courtesy of GENERAL MOTORS CORP.