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.
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HOMESERVICE MANUALSPONTIAC1997GRAND PRIX GTP, 4D SEDANREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 7 (BODY CONTROL MODULE)DIAGNOSIS & REPAIRDTC U1255, LOSS OF CLASS 2 SERIAL DATA FAULT (GENERAL)TESTING
1997 Pontiac Grand Prix GTP, 4D Sedan
DTC U1255, Loss Of Class 2 Serial Data Fault (General): Testing
1997 Pontiac Grand Prix GTP, 4D SedanSECTION Testing
WARNING: This page is about a different car, the 1997 Buick Regal and 1997 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
- If BCM diagnostic system check was performed, go to next step. If BCM diagnostic system check was not performed, go to BCM DIAGNOSTIC SYSTEM CHECK .
- Turn ignition off. Connect scan tool. Turn ignition on. Using scan tool, attempt to establish communication with PCM. If scan tool communicates with PCM, go to next step. If scan tool does not communicate with PCM, go to appropriate TESTS W/CODES article in ENGINE PERFORMANCE section. Refer to menu below.
- Check class 2 serial data link for intermittent open, short to ground, short to voltage, or poor connections at BCM, PCM or splice pack SP205. If problem is found, repair as necessary and go to step 6). If no problem is found, go to next step.
- Turn ignition off. Reinstall all components and connectors. Clear DTCs. Check for DTCs. If DTC U1255 sets again, go to next step. If DTC U1255 does not set again, system is operating properly.
- Turn ignition off. Replace BCM. See REMOVAL & INSTALLATION . Reprogram BCM. See BCM PROGRAMMING. Go to next step.
- Turn ignition off. Reinstall all components and connectors. Turn ignition on. Using scan tool, clear DTCs. Perform BCM DIAGNOSTIC SYSTEM CHECK .
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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.