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Home >> Lexus >> 1995 >> SC 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Engine Sensors & Switches >> Oxygen Sensor Operation >> Main Sensors
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Main Sensors

  1. Run the engine at 2500 RPM for about 2 minutes to warm the oxygen sensor. See CONNECTING TACHOMETER  under INTRODUCTION.
  2. Connect Jumper Wire (09843-18020) between terminals TE1 and E1 of DLC No. 1. See Figure. See COMPONENT LOCATIONS  under INTRODUCTION. Connect negative lead of analog voltmeter to terminal E1 of DLC No. 1. Connect positive lead to terminal VF1 (or VF2) of DLC No. 1. See IDENTIFYING VF1 & VF2 TERMINALS  table. Maintain engine speed at 2500 RPM.
    IDENTIFYING VF1 & VF2 TERMINALS (1)

    Application Oxygen Sensor
    VF1 Left
    VF2 Right
    (1) Terminals of Data Link Connector (DLC) No. 1. See Figure.
  3. Count how many times the voltmeter needle fluctuates in 10 seconds.
    • No fluctuations: go to step 8).
    • 8 or more fluctuations: oxygen sensor is okay.
    • Less than 8 fluctuations: go to next step.
  4. Run the engine at 2500 RPM for about 2 minutes to warm the oxygen sensor. Maintain engine speed at 2500 RPM. Count how many times the voltmeter needle fluctuates in 10 seconds.
    • No fluctuations: go to step 8).
    • 8 or more fluctuations: oxygen sensor is okay.
    • Less than 8 fluctuations: go to next step.
  5. Disconnect jumper wire from DLC No. 1. With engine speed at 2500 RPM, measure voltage between terminals E1 and VF1 (or VF2). If more than zero volts is indicated, replace oxygen sensor. If no voltage is indicated, retrieve and record trouble codes in normal mode and test mode, then go to next step. See appropriate TESTS W/CODES article.
  6. In test mode, if trouble codes other than Codes 21, 25, 26 and 28 are retrieved, perform procedure in TESTS W/CODES article. In normal mode, if Code 21, 25, 26 or 28 is retrieved, disconnect PCV hose. With engine speed at 2500 RPM, measure voltage between terminals E1 and VF1 (or VF2).
  7. If no voltage is indicated, replace oxygen sensor. If more than zero volts is indicated, fuel mixture is rich. Repair as necessary.
  8. Retrieve and record trouble codes in normal mode and test mode. See appropriate TESTS W/CODES article. In test mode, if trouble codes other than Codes 21, 25, 26 and 28 are retrieved, perform appropriate procedure in appropriate TESTS W/CODES article. In normal mode, if Code 21, 25, 26 or 28 is retrieved, disconnect jumper wire from DLC No. 1.
  9. With engine speed at 2500 RPM, measure voltage between terminals E1 and VF1 (or VF2). If about 5 volts is indicated, go to next step. If no voltage is indicated, disconnect PCV hose. With engine speed at 2500 RPM, measure voltage between terminals E1 and VF1 (or VF2). If no voltage is indicated, replace oxygen sensor. If more than zero volts is indicated, fuel mixture is rich. Repair as necessary.
  10. Disconnect ECT sensor connector. Connect a 4000-8000 ohm resistor across connector terminals. Connect jumper wire between terminals TE1 and E1 of DLC No. 1. Run the engine at 2500 RPM for about 2 minutes to warm the oxygen sensor.
  11. With engine speed at 2500 RPM, measure voltage between terminals E1 and VF1 (or VF2). If no voltage is indicated, replace oxygen sensor. If about 5 volts is indicated, fuel mixture is lean. Repair as necessary.
NOTE: When testing main sensors, if voltmeter needle did not fluctuate in step 2) and you ended up replacing the oxygen sensor, repeat step 2). Then, count how many times the voltmeter needle fluctuates in 10 seconds. If voltmeter needle does not fluctuate again, replace ECM.
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