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.
1999 Lexus SC 400FACTORY OEM SERVICE PROCEDURE
Engine Controls - Basic Diagnostic Procedures
- Introduction
- Preliminary Inspection & Adjustments
- Fuel System
- Notes
- Fuel Pump Operation
- Notes
- Checking Fuel Pump Operation Using Scan Tool (ES300 & RX300)
- Checking Fuel Pump Operation Using Scan Tool (GS300, GS400, SC300 & SC400)
- Checking Fuel Pump Operation Using Scan Tool (LS400)
- Checking Fuel Pump Operation Using Scan Tool (LX470)
- Checking Fuel Pump Operation By Applying Battery Voltage To Fuel Pump
- Fuel Pressure Release
- Fuel Pressure
- Fuel Pump Control Circuit
- Notes
- Circuit Opening Relay (ES300 & RX300)
- Circuit Opening Relay (LS400)
- EFI Main Relay (ES300 & RX300)
- EFI Main Relay (GS300 & GS400)
- EFI Main Relay (LS400)
- EFI Main Relay (LX470)
- EFI Main Relay (SC300 & SC400)
- Fuel Pump Electronic Control Unit (ECU) - (GS300 & GS400)
- Fuel Pump Electronic Control Unit (ECU) - (SC300 & SC400)
- Fuel Pump Electronic Control Unit (ECU) & Fuel Pump Switch (LX470)
- Fuel Pump Relay & Fuel Pump Resistor (LS400)
- Ignition Checks
- Idle Speed & Ignition Timing
- Summary
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.
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