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Home >> Chrysler >> 1995 >> LHS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 3.5L >> Test NTC-7A >> Checking Oxygen Sensor (O2S) Switching
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Checking Oxygen Sensor (O2S) Switching

NOTE: Scan tool displays left oxygen sensor as O2 and right oxygen sensor as O2R. After each repair, perform TEST VER-2  .
  1. Allow engine to reach normal operating temperature. Using scan tool, read O2S states (left and right). Increase engine speed to more than 1500 RPM. If O2S states are switching, system is functioning okay. Test is complete. If O2S states are not switching, check if O2S is locked on lean. If O2S is locked on lean, go to TEST NTC-7B. If O2S is not locked on lean, go to next step.
    WARNING: High fuel pressure may be present in fuel lines. Open fuel system with caution. See FUEL PRESSURE RELEASE  .
  2. Turn engine off. Release fuel pressure. Install fuel pressure gauge in fuel supply line. Turn ignition on. Using scan tool, actuate fuel system test. Allow fuel pressure gauge to stabilize to normal fuel pressure. Stop fuel system actuation test. Go to next step.
  3. Monitor fuel pressure gauge for one minute. If fuel pressure gauge reading drops more than 10 psi, replace leaking injector(s) or "O" rings as needed. If fuel pressure gauge reading does not drop more than 10 psi, go to next step.
  4. Inspect air cleaner and inlet ducts for restriction(s). Repair as required. If no restrictions are observed, go to TEST NTC-16A  .
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