Oxygen Sensor: Testing and Inspection

1984 Plymouth Horizon L4-97 1.6L SOHCSECTION Testing and Inspection

1. Apply parking brake, start engine and increase speed to 2000 RPM on front wheel drive models and 1500 RPM on rear wheel drive models. Make sure carburetor switch is not grounded.
2. Connect voltmeter to green solenoid output wire going to carburetor.
3. To perform full rich test, hold choke blades closed. During the next 10 seconds, voltage should decrease to 5 volts or less and remain there. If engine does not respond, proceed to step 4.
4. To perform full lean test, disconnect PCV system at vacuum source. During the next 10 seconds, voltage should increase to at least 9 volts and remain there until vacuum hose is reconnected.
5. If sensor fails tests in steps 3 and 4, replace. Reconnect all hoses and wires.


RENDER: 1.0x

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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.