GM Service Manual Online
For 1990-2009 cars only

Circuit Description

When the ignition switch is turned to ON, the sensing and diagnostic module (SDM) will perform a turn-on test to diagnose critical malfunctions within the SDM itself.

Conditions for Setting the DTC

The SDM does not implement diagnostic operation. In case of the above, the wiring harness of the SDM should be inspected before replacing the SDM.