Brake Warning Indicator Always On

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, 2004 Chevrolet Cab & Chassis Silverado, and 2003 GMC Sierra. However, it is still accessible from the selected car via links, so may be relevant.

Step	Action	Yes	No
Schematic Reference: Brake Warning System Schematics Connector End View Reference: Hydraulic Brakes Connector End Views , ABS Connector End Views in Antilock Brake System, and Body Control System Connector End Views in Body Control System
1	Did you review the Brake Warning System Description and Operation and perform the necessary inspections?	Go to Step 2	Go to Symptoms - Hydraulic Brakes
2	Turn OFF the ignition for 5 seconds. Ensure the park brake is released. Turn ON the ignition while observing the brake warning indicator. Does the brake warning indicator illuminate for 3 seconds and then turn OFF?	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 3
3	Install a scan tool. Select the Instrument Panel Cluster Special Functions menu on the scan tool. Command the Brake Lamp OFF. Does the brake warning indicator turn OFF?	Go to Step 4	Go to Step 11
4	Select Input 1 from the Body Control Module Data Display menu on the scan tool. Ensure the park brake is released. Observe the Park Brake status on the scan tool. Does the scan tool display Released?	Go to Step 5	Go to Step 6
5	Disconnect the brake fluid level switch or brake pressure differential switch harness connector if equipped. Does the brake warning indicator turn OFF?	Go to Step 12	Go to Step 8
6	Disconnect the park brake switch harness connector. Does the brake warning indicator turn OFF?	Go to Step 9	Go to Step 7
7	Disconnect from the body control module (BCM), the harness connector containing the park brake switch output circuit. Test the park brake switch output circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 14	Go to Step 10
8	Disconnect from the electronic brake control module (EBCM), the harness connector containing the brake fluid level sensor signal circuit or brake pressure differential switch, if equipped. Test the brake fluid level sensor signal circuit or brake pressure differential switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 14	Go to Step 13
9	Replace the park brake switch. Refer to Park Brake Warning Lamp Switch Replacement in Park Brake. Did you complete the replacement?	Go to Step 14	-
10	IMPORTANT: Perform the set up procedure for the BCM. Replace the BCM. Refer to Body Control Module Replacement in Body Control System.Did you complete the replacement?	Go to Step 14	-
11	Replace the instrument panel cluster. Refer to Instrument Panel Cluster (IPC) Replacement in Instrument Panel, Gages, and Console. Did you complete the replacement?	Go to Step 14	-
12	Replace the brake fluid level switch or the brake pressure differential switch, if equipped. Refer to Master Cylinder Reservoir Replacement . Did you complete the replacement?	Go to Step 14	-
13	IMPORTANT: Following EBCM replacement, use the scan tool to perform the Tire Size Calibration procedure. Replace the EBCM. Refer to Electronic Brake Control Module Replacement in Antilock Brake System.Did you complete the replacement?	Go to Step 14	-
14	Turn OFF the ignition for 5 seconds. Ensure the park brake is released. Turn ON the ignition while observing the brake warning indicator. Does the brake warning indicator illuminate for 3 seconds and then turn OFF?	System OK	Go to Step 2