03 Chevy 2500HD Service Brake System Warning

If the brake warning light is on then you may have a problem with the hydraulic system or a defective brake warning switch. Make sure that the emergency brake is fully released. Make sure there is enough fluid in the master cylinder.

Problem with brake system. Check fluid level.

check fuses first, cab and bay
if all good
scan the PCM .
or get it scanned.

Hello Kammy ,you have electronic problems ! Your best bet would have it towed to a qualified repair shop .
SERVICE BRAKE SYSTEM
Refer to Brake Warning System Description and Operation !
The instrument panel cluster (IPC) illuminates the brake warning indicator when one or more of the following occurs:
• The body control module (BCM) detects that the park brake is engaged. The IPC receives a class 2 message from the BCM requesting illumination.
• The electronic brake control module (EBCM) detects a low brake fluid condition. The IPC receives a class 2 message from the EBCM requesting illumination.
• The EBCM detects an ABS malfunction which disables dynamic rear proportioning (DRP). The IPC receives a class 2 message from the EBCM requesting illumination.
• The IPC performs the bulb check at the start of each ignition cycle. The brake warning indicator illuminates for approximately 3 seconds before turning OFF.
• The IPC detects a loss of class 2 communications with the BCM or with the EBCM.

When there are electronic problems the computers will not allow the vehicle to start , hooking up a factory or professional scan tool to see what the problem is is the first place to start .

SERVICE BRAKE BOOSTER
Refer to Brake Warning System Description and Operation in Hydraulic Brakes

SERVICE BRAKE BOOSTER
The SERVICE BRAKE BOOSTER message will be displayed when the supplemental brake assist signal circuit is toggled at 1.0 Hz with a 50 percent duty cycle. This message is also displayed if the instrument panel cluster (IPC) does not see an alive and well signal at key on. When this message is displayed it indicates a problem with the SBA and should be serviced or replaced.

How do the power brakes work ? Good .?

Service Brake Booster Message Displayed
Step
Action
Yes
No
Schematic Reference: Brake Warning System Schematics
1
Did you review the Brake Warning System Description and Operation and the Brake Assist System Description and Operation and perform the necessary inspections?
YES - Go to Step 2
NO - Go to Symptoms - Hydraulic Brakes
2
Start the vehicle.
Is the REDUCED BRAKE POWER message displayed for 1 minute before the SERVICE BRAKE BOOSTER message is displayed?
YES - Go to Step 3
NO - Go to Step 4
3
Perform the Brake Assist System Diagnosis
Did you find and correct the condition?
YES - Go to Step 12
NO - Go to Step 11
4
Disconnect the Supplemental Brake Assist connector.
Test the ignition 1 circuit for an open or a short to ground.
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
YES - Go to Step 12
NO - Go to Step 5
5
Test both ground circuits for opens.
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
YES - Go to Step 12
NO - Go to Step 6
6
Test the engine on signal circuit for an open or a short to ground.
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
YES - Go to Step 12
NO - Go to Step 7
7
Test the vehicle speed signal circuit for an open.
Did you find and correct the condittion?
YES - Go to Step 12
NO - Go to Step 8
8
Test the supplemental brake assist signal circuit for an open or a short to voltage.
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
YES - Go to Step 12
NO - Go to Step 9
9
Connect the supplement brake assist connector.
Disconnect the instrument panel cluster connector.
Connect a DMM from battery positive voltage to the supplemental brake assist signal circuit.
Turn the ignition to the RUN position while observing the DMM.
Did the DMM flash battery voltage?
YES - Go to Step 11
NO - Go to Step 10
10
Replace the Supplemental Brake Assist pump motor assembly Refer to Power Brake Booster Auxiliary Pump Replacement .
Did you complete the replacement?
YES - Go to Step 12
--
11
Replace the instrument panel cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gages and Console.
Did you complete the replacement?
YES - Go to Step 12
--
12
Start the engine.
Does the Service Brake Booster message stay on?
Go to Step 2
System OK

Check the warning sensor adjustment as the eb system may be worn enough to set it off if the adjustment is too close.

check that the brake is full off and that the switch is correctly adjusted.

Possibly a defective ABS sensor, or low brake fluid. Recommend a reputable mechanic to assess the issue.

1. Set parking brake and disconnect battery ground cable.
2. Discharge and recover system refrigerant. Refer to: "Service and Repair" See: Service and Repair
3. Disconnect all engine compartment heater and air conditioning lines and vacuum hoses.
4. Drain engine coolant and plug lines. Refer to: "Engine, Cooling and Exhaust : Cooling System : Service and Repair" See: Engine, Cooling and Exhaust\Cooling System\Service and Repair
5. Remove instrument panel. Refer to: "Instrument Panel, Gauges and Warning Indicators : Instrument Panel : Service and Repair" . See: Instrument Panel, Gauges and Warning Indicators\Instrument Cluster / Carrier\Service and Repair
6. Disconnect air conditioning hanger strap and temporarily reposition.
7. Remove rubber condensate drain tube and four mounting nuts in engine compartment.
8. Pull heater/air conditioning assembly to rear until unit studs clear dash panel, then drop unit down and remove from vehicle.
9. Place heater/air conditioning assembly on suitable workbench, then remove screw at vacuum harness and feed harness through hole in cover.
10. Remove thirteen screws from top cover, then remove top cover.
11. Remove screw from heater core tube retaining bracket, then lift heater core out of unit.
12. Remove evaporator core from unit.
13. Reverse procedure to install.

I have an '03 Chevy Tahoe and I had a similar problem. I discovered that there is a bare copper striking plate or tab that the medal emergency parking brake pedal touches when the emergency brake is set. It turns on the idiot brake light in the dash. It had broken off and the light stayed on all the time with the say issue of chiming whenever the vehicle is in motion. You or the dealership must replace that striker plate to fix the problem.