1999 Lexus SC 400FACTORY OEM SERVICE PROCEDURE

Checking Fuel Pump Operation Using Scan Tool (LX470)

  1. Connect scan tool to data link connector No. 3. See Figure. Turn ignition on. DO NOT start engine.
  2. Turn scan tool on. Select ACTIVE TEST MODE on scan tool. Using scan tool manufacturer's instructions, activate fuel pump. Remove intake manifold cover located on top of engine, above intake manifold. Intake manifold cover must be removed for access to fuel pressure pulsation damper located at firewall end of driver's side fuel rail. See Fig 1.
  3. Listen for operating sound at fuel pump and check that screw at center of fuel pressure pulsation damper moves upward due to the fuel pressure. See Fig 1. If fuel pump operates, check fuel pressure. See FUEL PRESSURE .
  4. If fuel pump does not operate, EFI main relay, fuel pump Electronic Control Unit (ECU) or fuel pump switch may be defective, or fuel pump switch may need to be reset. For explanation of EFI main relay, fuel pump ECU and fuel pump switch operation, or resetting of fuel pump switch, see FUEL PUMP CONTROL CIRCUIT . For testing of EFI main relay or fuel pump switch, see appropriate SYSTEM & COMPONENT TESTING article.
  5. If EFI main relay and fuel pump switch are okay, check for defective fuses or wiring. See appropriate wiring diagram in WIRING DIAGRAMS article. If fuses and wiring are okay, check for defective fuel pump. See CHECKING FUEL PUMP OPERATION BY APPLYING BATTERY VOLTAGE TO FUEL PUMP . If problem exists in fuel pump ECU or control circuit, Diagnostic Trouble Code (DTC) P1200 may be stored in Engine Control Module (ECM). See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article for retrieving of DTCs.
Fig 1: Locating Fuel Pressure Pulsation Damper & Screw (LX470)
G98J01607Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

Shop Manual-Ready ToolsCompare Repair QuoteQuote Shield Pro

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.

Rather have a pro handle this?

A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.

Comes to youSame-day available12-month warranty
Get a Free Quote

No obligation. See pricing before you book.