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 MANUALSCHEVROLET1987CHEVY VAN G20, 6.2 C, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISCCC TBI TESTS W/CODESDIAGNOSTIC CHARTSCODE 13 - OXYGEN SENSOR CIRCUIT ("SCAN" DIAGNOSTICS)DIAGNOSTIC AIDS

1987 Chevrolet Chevy Van G20, 6.2 C, Automatic

Diagnostic Aids

1987 Chevrolet Chevy Van G20, 6.2 C, AutomaticSECTION Diagnostic Aids

Normal "SCAN" voltage varies between 100-999 millivolts (.10-l.0 volt) while in "Closed Loop". Code 13 sets in one minute if voltage remains between .35-.55 volt, but system will go "Open Loop" in about 15 seconds. See INTERMITTENT TROUBLE CODES in TROUBLE SHOOTING Section.

Fig 1: Code 13, Oxygen (O2) Sensor Circuit ("SCAN" Diagnostics)

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.