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 MANUALSLEXUS1998SC 300REPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - SYSTEM/COMPONENT TESTS
1998 Lexus SC 300
Engine Controls - System/Component Tests
1998 Lexus SC 300SECTION Engine Controls - System/Component Tests
- Introduction
- Component Location
- Connector Identification
- Acoustic Control Induction System (ACIS)
- ACIS System Check
- Intake Air Control Valve (ES300, GS300 & SC300)
- Intake Air Control Valve (GS400 & SC400)
- Intake Air Control Valve (LS400)
- ACIS Vacuum Tank (ES300, GS300 & SC300)
- ACIS Vacuum Tank (GS400, LS400 & SC400)
- ACIS Vacuum Switching Valve (ES300, GS300 & SC300)
- ACIS Vacuum Switching Valve (GS400 & SC400)
- ACIS Vacuum Switching Valve (LS400)
- ACIS System Check
- Computerized Engine Controls
- Engine Sensors & Switches
- Notes
- Air-Fuel Ratio (AF) Sensor Heater Resistance (Es300, CALIFORNIA Models Only)
- Accelerator Pedal Position Sensor
- Camshaft Sensors
- Crankshaft Sensor
- Exhaust Gas RECIRCULATION (EGR) Temperature Sensor
- Exhaust Gas RECIRCULATION (EGR) Position Sensor
- Engine Coolant Temperature (ECT) Sensor
- Intake Air Temperature (IAT) Sensor
- Knock Sensor
- Mass Airflow (MAF) Sensor
- Oxygen Sensor Heater Resistance
- Oxygen Sensor Operation
- Park/Neutral Position (PNP) Switch
- Park/Neutral Position (PNP) Switch Circuit
- Throttle Position (TP) Sensor
- Vapor Pressure Sensor Circuit
- Variable Valve Timing Sensor
- Vehicle Speed Sensor (VSS)
- Modules, Motors, Relays & Solenoids
- Fuel System
- Idle Control System
- Ignition System
- Emission Systems & Sub-Systems
- Notes
- Exhaust Gas RECIRCULATION (EGR) System
- Exhaust Gas RECIRCULATION (EGR) Position Sensor
- Exhaust Gas RECIRCULATION (EGR) Vacuum Switching Valve (VSV)
- Exhaust Gas RECIRCULATION (EGR) Valve
- Exhaust Gas RECIRCULATION (EGR) Temperature Sensor
- Exhaust Gas RECIRCULATION (EGR) Vacuum Control Valve (VCV)
- Fuel Evaporation
- EVAP Canister (ES300)
- EVAP Canister (GS300 & GS400)
- EVAP Canister (LS400)
- EVAP Canister (SC300 & SC400)
- EVAP Vacuum Switching Valve (VSV) ES300
- EVAP Vacuum Switching Valve (VSV) GS300 & GS400
- EVAP Vacuum Switching Valve (VSV) SC300 & SC400
- EVAP Vacuum Switching Valve (VSV) LS400
- Vapor Pressure Sensor
- Vapor Pressure Sensor Vacuum Switch Valve (VSV) (Except ES300)
- Positive Crankcase Ventilation (PCV)
- Throttle Controls
- Variable Valve Timing (VVT) System
- Miscellaneous Controls
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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.