Code 21 (Chart 1), Steering Column Resistance Too High: Description

WARNING: This page is about a different car, the 1991 Geo Storm, 1991 Geo Metro, 1990 Geo Storm, and 1990 Geo Metro. However, it is still accessible from the selected car via links, so may be relevant.

DERM injects a current of 75 milliamperes through steering column from FORCE HI output (terminal No. A4) to FORCE LOW input (terminal No. A10). By monitoring voltage at SENSE HI input (terminal No. A7) and SENSE LOW input (terminal No. A6), DERM calculates combined resistance of inflator module, SIR coil, harness wiring (circuits No. 347 and 349) and connector terminal contact in steering column. Code 21 will set if resistance is greater than a specified value or 100-ohm resistor within resistor module is shorted.