Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSPLYMOUTH1984HORIZON BASE, 1.6 AREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 5 (ENGINE CONTROLS - TESTS W/CODES - 3.3L)DIAGNOSTIC CHARTSTEST NTC-7B - CHECKING OXYGEN (O2) SENSOR SWITCHING
1984 Plymouth Horizon Base, 1.6 A
Test NTC-7B - Checking Oxygen (O2) Sensor Switching
1984 Plymouth Horizon Base, 1.6 ASECTION Test NTC-7B - Checking Oxygen (O2) Sensor Switching
WARNING: This page is about a different car, the 1994 Eagle Vision, 1994 Dodge Intrepid, and 1994 Chrysler Concorde. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
For connector terminal identification, see CONNECTOR IDENTIFICATION DIRECTORY . For wiring diagrams, see WIRING DIAGRAMS section. After each repair, perform TEST VER-2 .
- Allow engine to idle. Inspect engine for vacuum leaks. Repair vacuum leaks as necessary. If no vacuum leaks exist, go to next step.
- Using DRB, read both O2 sensor signal voltages. If voltage for either or both O2 sensors is more than 0.1 volt, go to step 5). If voltage is less than 0.1 volt for both O2 sensors, go to next step.
- Turn ignition off. Disconnect faulty O2 sensor connector (left or right). Disconnect Powertrain Control Module (PCM) connector. PCM is located under air cleaner. Go to next step.
- Using DRB in ohmmeter mode, check resistance of left O2 sensor connector terminal No. 2 (Black/Dark Green wire) or right O2 sensor connector terminal No. 2 (Tan/White wire). If resistance at either or both O2 sensors is less than 10 ohms, repair short to ground in Black/Dark Green wire or Tan/White wire. If resistance is more than 10 ohms, replace O2 sensor.
- If voltage for either or both O2 sensors is more than 0.1 volt in step 2), turn engine off. Replace O2 sensor(s). Turn ignition on. Using DRB, reset adaptive fuel memory. Start engine, and allow it to reach normal operating temperature. Go to next step.
- Using DRB, read right and left O2 sensor states. If both O2 sensor states are switching, repair is complete. If both O2 sensor states are not switching, go to TEST NTC-15A .
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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.