Circuit/System Testing
WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the harness connector at the generator.
- Ignition ON, engine OFF, connect a test lamp to B+ and repeatedly probe the generator field duty cycle circuit terminal 2, while monitoring the GEN-F Terminal Signal Parameter. The parameter should change from 0 percent to above 95 percent.
- If the parameter was not affected by the test lamp, test the circuit for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the ECM.
- If the circuit tests normal, test or replace the generator.