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Engine Controls - System & Component Testing: Overview Lexus SC II

Testing & Diagnostics 2 illustrations ~1042 words

HEATED OXYGEN SENSOR OPERATION

If circuit or component is faulty, a Diagnostic Trouble Code (DTC) should set. Retrieve DTCs and perform appropriate diagnostic test. See appropriate SELF-DIAGNOSTICS article.

Fuel Pump Operation (Using Battery Voltage)

  1. Remove rear seat cushion. Remove fuel pump access cover. Remove floor service hole cover. Disconnect 5-pin connector from fuel pump and sending unit assembly. Connect a fused jumper wire between fuel pump connector terminal No. 5 and ground. (Scheme 184)
  2. Connect one end of second fused jumper wire to fuel pump connector terminal No. 4 first and then connect other end of fused jumper wire to battery voltage. Do not apply battery voltage to fuel pump for more than 10 seconds.
  3. On GS300 and IS300, check that fuel pressure pulsation damper screw rises when fuel pump operates. (Scheme 185) On GS430, LS430 and SC430, fuel pump is operating if fuel pump operating sound can be heard or pulsations can be felt in fuel inlet line near fuel rail. On all models, if fuel pump does not operate, replace fuel pump.

Scheme 184

Scheme 184
Scheme 184

Scheme 185

Scheme 185
Scheme 185

Fuel Injector Operation

Remove engine cover. Using a stethoscope, listen for clicking from each injector (or feel injector for vibration using a screwdriver) with engine running or cranking. If clicking is not heard, check for loose connection at fuel injector connector or fuel injector resistance. See «FUEL INJECTOR RESISTANCE». If fuel injector is okay, check for no voltage signal at suspect injector connector.

FUEL CUT SYSTEM OPERATION

Note. Information for SC430 is not available from manufacturer.

VARIABLE VALVE TIMING (VVT) SYSTEM OPERATION

If VVT system circuits or components are faulty, a Diagnostic Trouble Code (DTC) should set. See appropriate SELF-DIAGNOSTICS article.

Throttle System Operation (GS300 & IS300)

  1. Ensure all accessories are off. Ensure throttle linkage moves smoothly. Turn ignition on. Rotate accelerator pedal position sensor lever and listen for running sound from throttle motor. Ensure friction sound does not exist. If running sound exists, go to step 3. If friction sound exists or running sound does not exist, go to next step.
  2. Check throttle control motor. See «THROTTLE CONTROL MOTOR (GS300 & IS300)» under MOTORS, RELAYS & SOLENOIDS. Replace throttle control motor as necessary and retest. If throttle control motor is okay, check for open or short circuit in wiring harness between throttle control motor and ECM. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair wiring as necessary. If wiring is okay, ECM may be defective. Check ECM. See appropriate «PIN VOLTAGE CHARTS» article. Repair as necessary.
  3. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. see scheme 10 Using scan tool, select CURRENT DATA. Rotate accelerator pedal position sensor lever to full open position. Throttle opening percentage (THROTTLE POS on Lexus scan tool) should indicate 60 percent or more. If results are as specified, go to step 6. If results are not as specified, go to next step.
  4. Check throttle position sensor. See «THROTTLE POSITION (TP) SENSOR» under SENSORS & SWITCHES. Replace throttle position sensor as necessary and retest. If throttle position sensor is okay, check for open or short circuit in wiring harness between throttle position sensor and ECM. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair wiring as necessary. If wiring is okay, go to next step.
  5. Check accelerator pedal position sensor. See «ACCELERATOR PEDAL POSITION SENSOR» under SENSORS & SWITCHES. Replace accelerator pedal position sensor as necessary and retest. If accelerator pedal position sensor is okay, check for open or short circuit in wiring harness between accelerator pedal position sensor and ECM. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair wiring as necessary. If wiring is okay, go to next step.
  6. Start engine. Allow engine to reach normal operating temperature. Ensure all accessories are off. Place transmission in Neutral position. Turn A/C on and then off and check idle speed. Idle speed should be between 700-800 RPM with A/C on. Idle speed should be between 650-750 RPM with A/C off.
  7. With engine idling, pinch air assist hose located next to throttle motor. Idle speed should drop and return back to normal. If idle speed changes as specified, no problem is indicated at this time. If idle speed does not change as specified, check throttle body. If throttle body is okay, check for open or short circuit in wire harness. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair wiring as necessary. If wiring is okay, ECM may be defective. Check ECM. See «PIN VOLTAGE CHARTS» article. Repair as necessary. After repair is completed, drive vehicle to ensure vehicle performs properly.

Throttle System Operation (GS430 & LS430)

  1. Remove engine cover. Ensure throttle linkage moves smoothly. Turn ignition on. Depress and release accelerator pedal several times and listen for smooth running sound from throttle control motor. If throttle control motor operates smoothly, go to step 3 . If throttle control motor does not operate smoothly or cannot be heard at all, go to next step.
  2. Check throttle control motor operation. See «Throttle Control Motor (GS430, LS430 & SC430)» under MOTORS in MOTORS, RELAYS & SOLENOIDS. Replace as necessary. If throttle control motor operation is as specified, check for open or short circuit in wiring between throttle control motor and ECM. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If wiring is okay, go to next step.
  3. Check throttle position sensor operation. See «THROTTLE POSITION (TP) SENSOR» under SENSORS & SWITCHES. Replace as necessary. If throttle position sensor operation is as specified, check for open or short circuit in wiring between throttle position sensor and ECM. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Repair as necessary. If wiring is okay, go to next step.
  4. Check accelerator pedal position sensor operation. See «ACCELERATOR PEDAL POSITION SENSOR» under SENSORS & SWITCHES. Replace as necessary. If accelerator pedal position sensor operation is as specified, check for open or short circuit in wiring between accelerator pedal position sensor and ECM. See appropriate WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, ECM may be defective. Check ECM. See «PIN VOLTAGE CHARTS» article. Repair as necessary.

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