1992 Lexus SC 400FACTORY OEM SERVICE PROCEDURE

Spark Test

  1. Remove coil wire from distributor. Using insulated pliers, hold end of coil wire 1/2" from ground. Crank engine. If spark is present, see appropriate DIAGNOSIS BY SYMPTOM in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
  2. If spark is not present, turn ignition off. Check ignition coil, ignitor and distributor connectors. Repair as necessary.
  3. If connectors are okay, check resistance of high tension cables. Maximum resistance is 25,000 ohms per cable. Replace as necessary. If resistance is within specification, go to next step.
  4. Turn ignition on. Using a DVOM, ensure battery voltage is present at ignition coil positive terminal. If battery voltage is not present, check wiring between ignition switch and ignition coil. If battery voltage is present, go to next step.
    NOTE: LS400 and SC400 have 2 ignition coils.
  5. Turn ignition off. Using a DVOM, measure resistance of ignition coil (cold). Positive terminal on ignition coil has a tab next to terminal. See IGNITION COIL RESISTANCE table. If resistance is not within specification, replace ignition coil. If resistance is within specification, go to step 6) for ES300 and SC300 or step 9) for LS400 and SC400.
    IGNITION COIL RESISTANCE

    Application Primary Secondary
    ES300 .30-.60 9000-15,000
    LS400 & SC400 .40-.50 10,200-13,800
    SC300 .20-.30 6000-11,000
  6. On ES300 and SC300, measure resistance of pick-up coil. See Fig 1. See DISTRIBUTOR SENSOR RESISTANCE table. If resistance is not within specification, replace distributor housing assembly.
  7. Check air gap in distributor. Measure air gap of G1 pick-up, G2 pick-up and NE pick-up. See Fig 2. Air gap specification for ES300 is .008-.020" (.2-.5 mm). Air gap specification for SC300 is .008-.016" (.2-.4 mm). If air gap is not to specification, replace distributor.
  8. If air gap is to specification, perform appropriate trouble shooting procedures in TESTS W/CODES article in the ENGINE PERFORMANCE Section. If voltage reading and wiring harness are okay, substitute ignitor with a known good unit.
    DISTRIBUTOR SENSOR RESISTANCE

    Application Ohms
    ES300 & SC300
    Pick-Up Coils
    Between Terminals G1 & G 125-190
    Between Terminals G2 & G 125-190
    Between Terminals NE & G 155-240
    LS400
    No. 1 & No. 2 Cam Sensors 950-1250
    Engine Speed Sensor 950-1250
    SC400
    No. 1 & No. 2 Cam Sensors 835-1350
    Engine Speed Sensor 835-1350
    Fig 1: Identifying Pick-Up Coil Connectors (ES300 & SC300)
    G92D26123Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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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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