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 MANUALSCHEVROLET1987HI-CUBE 6.2 J, 475/M40REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 15 (ENGINE CONTROLS - SYSTEM/COMPONENT TESTS - GASOLINE)ENGINE SENSORS & SWITCHESENGINE CONTROLS - SYSTEM/COMPONENT TESTS - GASOLINEOXYGEN SENSOR
1987 Chevrolet Hi-Cube 6.2 J, 475/M40
Oxygen Sensor
1987 Chevrolet Hi-Cube 6.2 J, 475/M40SECTION Oxygen Sensor
WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Yukon, 1994 GMC Suburban, 1994 GMC Pickup, 1994 GMC Cab & Chassis, and 1994 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
- Start engine and warm to operating temperature. Disconnect oxygen sensor. Connect DVOM between Purple lead of oxygen sensor and ground. Place DVOM on 2-volt scale.
- Using another DVOM on 20-volt scale, connect voltmeter in series between Purple wire from ECM and positive post of battery. This will simulate a rich condition, causing ECM to respond by leaning mixture. Reading on voltmeter connected to oxygen sensor should decrease to less than .3 volt.
- Move voltmeter lead from positive battery post to negative battery post. This will simulate a lean condition, causing ECM to respond by richening mixture. Reading on voltmeter connected to oxygen sensor should increase to greater than .8 volt. If reading does not change as specified, replace oxygen sensor.
- If a second DVOM is not available, install a jumper in Purple wire from ECM. Hold jumper in one hand and touch positive post of battery with other hand to simulate a rich condition. Touch negative post of battery to simulate a lean condition. For additional testing procedures, see appropriate TESTS W/CODES
article in the ENGINE PERFORMANCE section below.
- G - TESTS W/CODES - 4.3L
- G - TESTS W/CODES - 5.0L
- G - TESTS W/CODES - 5.7L
- G - TESTS W/CODES - 7.4L
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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.