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 C1276: Serial Data Malfunction
1998 Buick RivieraSECTION DTC C1276: Serial Data Malfunction
- Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK. After performing diagnostic system check, go to next step.
- Install scan tool. Check if scan tool communicates with any control module other than EBCM/EBTCM. If scan tool communicates with other control modules, go to next step. If scan tool does not communicate with other control modules, diagnose serial data line. See appropriate diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS.
- Turn ignition off. Disconnect EBCM/EBTCM connector. Connect ABS pinout box to connector. Measure resistance between pinout box terminal No. 42 and ground. Also, measure resistance between pinout box terminal No. 23 and ground. If resistance is infinite, go to step 5) . If resistance is not infinite, go to next step.
- Repair short to ground in Tan wire or Tan/Black wire between instrument cluster, HVAC programmer and EBCM/EBTCM.
- Disconnect PCM connectors. Using DVOM, measure resistance between pinout box terminals No. 42 and 15 (Tan wire or Tan/Black wire) of PCM connector. Also, measure resistance between pinout box terminal No. 23 and terminal No. 15 (Tan wire or Tan/Black wire) of PCM connector. If resistance is 0-2 ohms for both measurements, go to step 7) . If resistance is not 0-2 ohms for both measurements, go to next step.
- Repair open or high resistance in Tan wire or Tan/Black wire between sensing diagnostic module, data link connector, instrument cluster, HVAC programmer and PCM.
- Turn ignition switch to START position. Using DVOM set on DC scale, measure voltage between pinout box terminal No. 42 and ground. If battery voltage is present, go to next step. If battery voltage is not present, go to step 9) .
- Repair short to voltage in Tan wire or Tan/Black wire between instrument cluster, HVAC programmer and EBCM/EBTCM.
- Replace PCM. Perform PCM relearn procedures.
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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.