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 MANUALSMERCURY1991TRACER BASE, 4D SEDAN, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 13 (ENGINE CONTROLS - TESTS W/CODES - EEC 1.8L)CIRCUIT TESTSCIRCUIT TEST O2S - OXYGEN SENSOR
1991 Mercury Tracer Base, 4D Sedan, Automatic
Circuit Test O2S - Oxygen Sensor
1991 Mercury Tracer Base, 4D Sedan, AutomaticSECTION Circuit Test O2S - Oxygen Sensor
WARNING: This page is about a different car, the 1994 Mercury Tracer and 1994 Ford Escort. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Enter this test only when Code 15 (lean) or Code 17 (rich) is displayed during self-test procedures (KOEO or KOER). This test is intended to diagnose O2S circuit.
RENDER: 1.0x
NO RELATED
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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.