Circuit/System Testing
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT:
If a glow plug is replaced and the tip is missing or burned off, the cylinder head must be removed and all debris be cleaned out of the cylinder.
- Ignition ON, and the glow plugs not commanded ON, probe the affected glow plug with a test lamp connected to ground. Observe that the test lamp does not illuminate.
- If the test lamp does illuminate, test the glow plug control circuit for a short to voltage or for a faulty glow plug control module (GPCM). Replace the affected glow plug after repair.
- Ignition ON, probe the affected glow plug with a test lamp connected to ground. Command the glow plugs ON with a scan tool and observe the test lamp. The test lamp should illuminate.
- If the test lamp does not illuminate, test the affected glow plug harness between the glow plug control module and the glow plug for an open, short to ground or high resistance.
- Ignition OFF, and the affected glow plug disconnected, measure the resistance between the affected glow plug terminal A and ground with a DMM for less than 1 ohm.
- If the resistance is more than 1 ohm, replace the affected glow plug.
- Ignition OFF, and the glow plug control module harness disconnected, measure the resistance between the affected glow plug harness connector terminal A and the corresponding glow plug control module harness connector terminal for less than 1 ohm resistance.
- If the resistance is more than 1 ohm, repair the harness.
- If the resistance is less than 1 ohm, replace the glow plug control module.