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Home >> Buick >> 2001 >> Century Limited >> Repair and Diagnosis >> Brakes >> Traction Control >> Anti-Lock Brake System With Traction Control System - DELPHI 7 >> Diagnostic Tests >> DTC C1277 Or DTC P1571: Requested Torque Signal Malfunction ("W" Body")

DTC C1277 Or DTC P1571: Requested Torque Signal Malfunction ("W" Body")

  1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK  under DIAGNOSIS & TESTING. After performing diagnostic system check, go to next step.
  2. Check EBCM and PCM ground. Ensure each ground is clean and tightened properly. Repair as necessary. After repairs, go to step  13. If grounds are okay, go to next step.
  3. Install scan tool. Start engine. Using scan tool, observe Torque Request Signal parameter in the PCM data list. If scan tool displays less than 100%, problem is intermittent. See INTERMITTENTS & POOR CONNECTIONS  under DIAGNOSIS & TESTING. If scan tool does not display 100%, go to next step.
  4. Turn ignition off. Disconnect EBCM harness connector. Install Universal Pinout Box (J-39700) using Cable Adapter (J-39700) to EBCM harness connector and EBCM. Start engine. Check DC duty cycle between the requested torque signal circuit and good ground. If duty cycle is within 5-95%, go to next step. If duty cycle is not within 5-95%, go to step  6.
  5. Measure DC Hz between requested torque signal circuit and a good ground. If frequency measures within 121-134 Hz, go to step  8. If frequency does not measure within 121-134 Hz, go to next step.
  6. Turn ignition off. Disconnect cable adapter from EBCM connector. Turn ignition on, with engine off. Check voltage from requested torque signal circuit to a good ground. If voltage reading is 4-6 volts, go to step  10. If voltage reading is not 4-6 volts, go to next step.
  7. Turn ignition off. Disconnect PCM harness connector. Check requested torque signal circuit for short to voltage or short to ground. Repair as necessary. After repairs, go to step  13. If circuit is okay, go to step  10.
  8. Turn ignition off. Disconnect PCM harness connector. Check requested torque signal circuit for open or high resistance. Repair as necessary. After repairs, go to step  13. If circuit is okay, go to next step.
  9. Check for poor connections at PCM harness connector. Repair as necessary. After repairs, go to step  13. If connections are okay, go to step  11.
  10. Check for poor connections at EBCM harness connector. Repair as necessary. After repairs, go to step  13. If connections are okay, go to step  12.
  11. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to step  13.
  12. Replace EBCM. After replacing EBCM, go to next step.
  13. Using scan tool, clear DTCs. Recheck DTCs. If DTC resets, go to step  2. If DTC does not reset, system is okay.
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