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 MANUALSCHEVROLET1997CHEVY EXPRESS G3500, VAN CARGO, 6.5 FREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 46 (ENGINE CONTROLS - SYSTEM/COMPONENT TESTS - 7.4L)ENGINE SENSORS & SWITCHESOXYGEN SENSOR (O2S)
1997 Chevrolet Chevy Express G3500, Van Cargo, 6.5 F
Oxygen Sensor (O2S)
1997 Chevrolet Chevy Express G3500, Van Cargo, 6.5 FSECTION Oxygen Sensor (O2S)
WARNING: This page does not describe the selected car, but rather 18 other vehicles, including the 1995 GMC Vandura Special, 1995 GMC Vandura, 1995 GMC Suburban, 1995 GMC Rally Camper Special, and 1995 GMC Rally. 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 DVOM in series between Purple wire from ECM/PCM/VCM and positive post of battery. This will simulate a rich condition, causing ECM/PCM/VCM to respond by leaning mixture. Reading on DVOM connected to oxygen sensor should decrease to less than .3 volt.
- Move DVOM lead from positive battery post to negative battery post. This will simulate a lean condition, causing ECM/PCM/VCM to respond by richening mixture. Reading on DVOM 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, connect a jumper in Purple wire from ECM/PCM/VCM. 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 TESTS W/CODES - 7.4L article.
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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.