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Home >> Saturn >> 2000 >> SC2 Automatic, MP6 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0508: Idle Control System Circuit Low >> Diagnostic Procedures
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Diagnostic Procedures

  1. Start and operate engine at idle. Using scan tool, monitor 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. Turn ignition off. Disconnect IAC tester. Disconnect PCM harness connector J1. Check continuity between ground and IAC valve harness connector terminals "A", "B", "C" and "D". If continuity does not exist on any of the circuits, go to next step. If continuity exists on any of the circuits, check and repair short to ground in affected circuit.
  4. Check continuity between each combination of the 4 IAC valve circuits for short to each other. Repair as necessary. If circuits are okay, replace PCM.
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