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Home >> Saturn >> 2000 >> SC1 Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0509: Idle Control System Circuit High >> Diagnostic Procedures
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Diagnostic Procedures

  1. Start and operate engine at idle. Using scan tool, monitor IAC MOTOR CKT. - OPEN or IAC MOTOR CKT. - LOW VOLT test while accelerating engine using accelerator pedal to 3500 RPM and slowly returning to idle. Repeat 5 times. Then, accelerate engine to 3500 RPM and snap throttle back to idle. Repeat 5 times. If scan tool indicates TEST FAIL, go to next step. If scan tool does not indicate TEST FAIL, problem is intermittent. See DIAGNOSTIC AIDS  .
  2. Allow engine to idle. Disconnect IAC valve harness connector. Connect IAC Tester (SA9195E) to IAC valve. Using tester, increase and decrease engine speed. If engine speed changes as commanded, go to next step. If engine speed does not change as commanded, replace IAC valve.
  3. Disconnect IAC tester. Reconnect IAC valve. Allow engine to idle. Disconnect IAC valve. Connect a test light to battery voltage and individually probe each IAC valve harness connector terminals while increasing and decreasing engine speed by moving throttle blade by hand. If test light pulses on each circuit when engine speed is increased or decreased, check terminal tightness at IAC valve. Repair as necessary. If terminals are okay, replace PCM. If test light does not pulse on a circuit when engine speed is increased or decreased, go to next step.
  4. Check affected circuit for open or short to voltage. Check for terminal tightness at PCM. Repair as necessary. If circuit or terminals are okay, replace PCM.
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