Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSSATURN2000SC2 AUTOMATIC, MP6REPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - SELF-DIAGNOSTICSDIAGNOSTIC TESTSDTC P0509: IDLE CONTROL SYSTEM CIRCUIT HIGHDIAGNOSTIC PROCEDURES
2000 Saturn SC2 Automatic, MP6
Diagnostic Procedures
2000 Saturn SC2 Automatic, MP6SECTION Diagnostic Procedures
- 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 .
- 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.
- 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.
- 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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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.