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Home >> Cadillac >> 1998 >> Eldorado Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P1571 - Traction Control System Pulse Width Modulated PWM) Circuit No Frequency >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then go to next step.
  2. Using scan tool, record any failure records and DTC information. Clear DTCs. Start and operate engine at idle for several minutes. Check for stored DTCs again. If DTC P1571 failed this ignition cycle, go to next step. If DTC P1571 did not fail in this ignition cycle, fault is not present. See DIAGNOSTIC AIDS.
  3. Turn ignition off. Disconnect EBTCM harness connector. Turn ignition on, engine off. Using DVOM, check voltage between ground and desired torque circuit at EBTCM connector terminal. If voltage reading is 4.8-5.4 volts, go to next step. If voltage reading is not 4.8-5.4 volts, go to step 6).
  4. Ensure EBTCM connector is still disconnected. Start and operate engine at idle. Using scan tool, monitor the desired torque output. Momentarily short the desired torque circuit to ground at EBTCM connector terminal. If scan tool display reading drops to near 0 torque when circuit is grounded, fault is in EBTCM system. Diagnose EBTCM system. See ANTI-LOCK BRAKE SYSTEM article in the BRAKES section. If scan tool reading does not drop, go to next step.
  5. Turn ignition off. Disconnect both PCM harness connectors. Check for short between desired torque circuit and all other 5-volt reference PCM circuits (i.e. TP sensor, EGR position sensor, MAP sensor). Repair as necessary. If circuits are okay, go to step 9).
  6. If voltage reading is greater than 5.4 volts, go to step 8). If voltage reading is not greater than 5.4 volts, go to next step.
  7. Turn ignition off. Disconnect both PCM harness connectors. Check for short to ground, open or short to another circuit on desired torque circuit. Repair as necessary. If circuit is okay, go to step 9).
  8. Check for short to voltage on desired torque output circuit. Repair as necessary. If circuit is okay, go to next step.
  9. Check PCM terminals. Repair as necessary. If terminals are okay, go to next step.
  10. Replace PCM. Program replacement PCM using required equipment.
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