Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC Display Order
1998 Pontiac Firebird V8-5.7L VIN GSECTION DTC Display Order
If DTC 12 and DTC 55 are displayed when the BCM is in the diagnostic mode, and no other DTCs are displayed, the BCM is operating properly.
In the diagnostic mode, diagnostic trouble codes (DTCs) are displayed in the following order:
1. DTC 12
2. Any current DTCs (DTC 21-DTC 25) or any history DTCs (DTC 31-DTC 35)
3. The remote control door lock transmitter diagnostic DTCs (DTC 41-DTC 45)
These DTCs will display if they are evoked while in the diagnostic mode.
4. The begin configuration display (DTC 55). DTC 55 and 2 configuration numbers are always displayed. The first number following DTC 55 is the hardware configuration. The second number is the software configuration.
5. After the configuration numbers are displayed, the entire list is repeated beginning with DTC 12.
DTC 12 is always set and displayed when the body control module (BCM) is in the diagnostic mode. DTC 12 indicates that the diagnostic function is in progress. DTC 55 is also always displayed.
If DTC 12 and DTC 55 are displayed when the BCM is in the diagnostic mode, and no other DTCs are displayed, the BCM is operating properly.
If DTC 12 and DTC 55 are not displayed when the BCM is in the diagnostic mode, refer to DTC 12 Diagnostic System Check. DTC 12
If any other DTCs are displayed, refer to Diagnostic Trouble Code (DTC) List/type. Body Control Module (BCM)
System faults are stored as current or history DTCs. When working on systems controlled by the body control module, always refer to Body Control Module and test for DTCs. Body Control Module
In the diagnostic mode, diagnostic trouble codes (DTCs) are displayed in the following order:
1. DTC 12
2. Any current DTCs (DTC 21-DTC 25) or any history DTCs (DTC 31-DTC 35)
3. The remote control door lock transmitter diagnostic DTCs (DTC 41-DTC 45)
These DTCs will display if they are evoked while in the diagnostic mode.
4. The begin configuration display (DTC 55). DTC 55 and 2 configuration numbers are always displayed. The first number following DTC 55 is the hardware configuration. The second number is the software configuration.
5. After the configuration numbers are displayed, the entire list is repeated beginning with DTC 12.
DTC 12 is always set and displayed when the body control module (BCM) is in the diagnostic mode. DTC 12 indicates that the diagnostic function is in progress. DTC 55 is also always displayed.
If DTC 12 and DTC 55 are displayed when the BCM is in the diagnostic mode, and no other DTCs are displayed, the BCM is operating properly.
If DTC 12 and DTC 55 are not displayed when the BCM is in the diagnostic mode, refer to DTC 12 Diagnostic System Check. DTC 12
If any other DTCs are displayed, refer to Diagnostic Trouble Code (DTC) List/type. Body Control Module (BCM)
System faults are stored as current or history DTCs. When working on systems controlled by the body control module, always refer to Body Control Module and test for DTCs. Body Control Module
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.