SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSBUICK2000CENTURY CUSTOMREPAIR AND DIAGNOSISBRAKESTRACTION CONTROLANTI-LOCK BRAKE SYSTEM WITH TRACTION CONTROL SYSTEM - DELPHI 7DIAGNOSTIC TESTSDTC C1277: REQUESTED TORQUE SIGNAL CIRCUIT MALFUNCTION
2000 Buick Century Custom

DTC C1277: Requested Torque Signal Circuit Malfunction

2000 Buick Century CustomSECTION DTC C1277: Requested Torque Signal Circuit Malfunction
  1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under DIAGNOSIS & TESTING. After performing diagnostic system check, go to next step.
  2. Install scan tool. Start engine. Using scan tool, observe DTC information parameter in PCM Diagnostic Trouble Codes (DTCs). If scan tool displays DTC P1571 as current, go to DTC P1571. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool does not display DTC P1571, go to next step.
  3. Check EBCM ground connections on transaxle stud, near starter. Ensure each ground is clean and tightened properly. Clean and retighten as necessary. After repairs, go to step  13 . If ground is okay, go to next step.
  4. Using scan tool, observe requested torque parameter in ABS/TCS data list. If scan tool displays a range of 5-95 percent, go to next step. If scan tool does not display a range of 5-95 percent, go to step  7 .
    NOTE: DO NOT turn ignition on while EBCM is disconnected.
  5. Turn ignition off. Disconnect EBCM harness connector. Install Universal Breakout Box (J 39700) using Cable Adapter (J 39700-99) to EBCM harness connector and EBCM. Start engine. Using a DVOM, measure DC Duty Cycle between the requested torque signal circuit and ground. If DVOM reading is 5-95 percent, go to next step. If DVOM reading is not 5-95 percent, go to step  7 .
  6. Measure DC Hz between the requested torque signal circuit and ground. If frequency is 121-134 Hz, go to step  11 . If frequency is not 121-134 Hz, go to step  10 .
  7. Check for open in requested torque signal circuit. Repair as necessary. After repairs, go to step  13 . If circuit is okay, go to next step.
  8. Check for short to ground in requested torque signal circuit. Repair as necessary. After repairs, go to step  13 . If circuit is okay, go to next step.
  9. Check for short to voltage in requested torque signal circuit. Repair as necessary. After repairs, go to step  13 . If circuit is okay, go to next step.
  10. Check EBCM harness connector for poor connections or terminal tension. Repair as necessary. After repairs, go to step  13 . If connections or terminals are okay, go to step  12 .
  11. Check PCM. Perform Powertrain On-Board Diagnostic (OBD) System Check. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. After performing OBD system check, go to step  13 .
  12. Replace EBCM. After replacing EBCM, go to next step.
  13. Using scan tool, clear DTCs. Turn ignition on and recheck for DTCs. If DTC resets, go to step  2 . If DTC does not reset, system is okay.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

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.