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Home >> Chevrolet >> 2000 >> Prizm Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics - 1.8L >> Diagnostic Tests >> DTC P1520: Stoplight Switch Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Turn ignition off. Ensure brake pedal is released and check operation of rear stoplights. If rear stoplights are illuminated, go to next step. If rear stoplights are not illuminated, go to step  5 .
  3. Disconnect stoplight switch harness connector. Check operation of rear stoplights. If stoplights are illuminated, go to next step. If stoplights are not illuminated, go to step  7 .
  4. Turn ignition off. Disconnect PCM harness connector. With stoplight switch disconnected, check voltage at stoplight switch connector brake signal circuit. See WIRING DIAGRAMS article. If voltage reading is zero volts, go to step  8 . If voltage reading is not zero volts, go to step  10 .
  5. Using a scan tool, monitor TCC brake switch parameter. Ensure brake pedal is released. If scan tool indicates stoplight switch is in released position, see DIAGNOSTIC AIDS  . If scan tool does not indicate stoplight switch is released, go to next step.
  6. Turn ignition off. Disconnect PCM harness connector. Back out PCM 22-pin connector brake signal circuit terminal. See WIRING DIAGRAMS article. Reconnect PCM connector with brake signal circuit wire terminal removed. Using scan tool, monitor TCC brake switch parameter. If scan tool indicates stoplight switch is in released position, go to step  8 . If scan tool does not indicate stoplight switch is released, go to step  10 .
  7. Check for a misadjusted stoplight switch. If stoplight switch is out of adjustment, go to step  11 . If stoplight switch adjustment is okay, go to step  9 .
  8. Repair short to voltage in brake signal circuit between PCM and stoplight switch. After repairs, go to step  11 .
  9. Replace stoplight switch. After replacing switch, go to step  11 .
  10. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  11. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTC(s).
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