1999 Lexus LS 400FACTORY OEM SERVICE PROCEDURE

Ignition Timing: GS400

  1. Remove intake manifold cover located on top of engine, above intake manifold. Start engine and warm engine to normal operating temperature. Shut engine off. Connect scan tool to data link connector No. 3. See Figure. Scan tool is used to read engine RPM.
  2. Connect timing light lead to Yellow wire at ignition coil electrical connector on top of driver's side valve cover at cylinder No. 1. See Fig 1. Cylinder No. 1 is front cylinder on left side of engine when viewed from flywheel end of engine. See Figure.
  3. Install Jumper Wire (SST 09843-18020) between terminals TC and E1 on data link connector No. 1. See Fig 2. Data link connector is located near driver's side strut tower.
  4. Apply parking brake. Place transmission in Neutral. Start engine and allow engine to idle.
  5. Timing marks are located on timing belt cover, near crankshaft pulley. Ensure base timing is 8-12 degrees BTDC at idle with transmission in Neutral, and with A/C and all accessories off. Shut engine off. Remove jumper wire, timing light and scan tool. Reinstall intake manifold cover.
    Fig 1: Connecting Timing Light At Ignition Coil (GS400)
    G99B50428Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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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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