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 MANUALSOLDSMOBILE1998ACHIEVA 3.1 M, 4T40E/MN4REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 6 (BODY CONTROL MODULES)DIAGNOSTIC TESTSDTC U1255: LOSS OF CLASS 2 SERIAL DATA FAULT (GENERAL)TESTING
1998 Oldsmobile Achieva 3.1 M, 4T40E/MN4
DTC U1255: Loss Of Class 2 Serial Data Fault (General): Testing
1998 Oldsmobile Achieva 3.1 M, 4T40E/MN4SECTION Testing
WARNING: This page is about a different car, the 1999 Buick Regal and 1999 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
- Perform Data Link Connector (DLC) diagnostic system check. Go to DLC DIAGNOSTIC SYSTEM CHECK under SYSTEM TESTS. After DLC diagnostic system check is performed, go to next step.
- 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 under SYSTEM TESTS.
- Turn ignition on. Using scan tool, clear DTCs. Check for DTCs. If DTC U1255 is set, go to next step. If DTC U1255 is not set, go to step 5 .
- Replace BCM. See BODY CONTROL MODULE (BCM) under REMOVAL & INSTALLATION. Reprogram BCM. See NEW BCM SETUP under PROGRAMMING. Go to step 6 .
- System is operating properly at this time. See DIAGNOSTIC AIDS . After any repairs are made, go to next step.
- Turn ignition off. Reinstall all components and connectors. Turn ignition on. Using scan tool, clear DTCs. Check for DTCs. If any DTCs are current, perform BCM DIAGNOSTIC SYSTEM CHECK under SYSTEM TESTS. If no DTCs are current, system is operating properly.
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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.