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 MANUALSCHEVROLET1994C 2500 SUBURBAN 2WD V8-350 5.7LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONCOMPONENT TESTS AND GENERAL DIAGNOSTICSOXYGEN SENSOR (O2S) TESTING
1994 Chevrolet C 2500 Suburban 2WD V8-350 5.7L
Oxygen Sensor (O2S) Testing
1994 Chevrolet C 2500 Suburban 2WD V8-350 5.7LSECTION Oxygen Sensor (O2S) Testing
VISUAL INSPECTION
- Connectors and wires
- Housing and insulator for cracks/damage
- Sensor tip for silicone contamination (white powdery coating)
CAUTION Do NOT perform the following test for more than 2 minutes,
as this may cause damage to the catalytic converter.
PERFORMANCE TEST
Checks working range and response (speed).
- Warm engine
- Install DVOM between sensor and ground (2 volt D.C. range)
- "RUN" engine at steady cruise speed (about 2500 rpm)
Voltage should vary at least eight times in ten seconds between 0.2 and 0.8 volts (normal range).
- Drive system rich: The use of a properly adjusted propane flow-meter (J-26911) is industry standard.
Voltage should increase to at least 0.8 volts within two to three seconds.
- Drive system lean: Create a vacuum leak from a source that is not an control module input or output.
Voltage should drop to at least 0.3 volts within two to three seconds.
NOTE After each test the O2 sensor should return to normal operating range within two to three seconds.
- O2 Sensor should be replaced for failure to pass any of the tests above.
NOTE A CEC system that is operating excessively rich or lean will drive the 02 sensor to its maximum range and should be repaired first and not diagnosed as a 02 sensor failure.
- Reconnect all hoses and electrical connectors. Clear all codes set and retrain idle.
HEATING ELEMENT (H20S only)
- Turn ignition "OFF". Disconnect electrical connector.
- Connect test light between harness terminals "A" and "B".
- Turn ignition "ON". Test light should be "ON".
- If test light is "OFF", connect test light to harness terminal "A" to ground. Light should be "ON" ensuring power circuit is operating correctly.
- Turn ignition "OFF".
- Using an ohmmeter, measure resistance between terminals A and B.
Resistance @ Specified Temperature
3.5 ohms @ 20°C (68°F)
14 ohms @ 350°C (662°F)
- Connectors and wires
- Housing and insulator for cracks/damage
- Sensor tip for silicone contamination (white powdery coating)
CAUTION Do NOT perform the following test for more than 2 minutes,
as this may cause damage to the catalytic converter.
PERFORMANCE TEST
Checks working range and response (speed).
- Warm engine
- Install DVOM between sensor and ground (2 volt D.C. range)
- "RUN" engine at steady cruise speed (about 2500 rpm)
Voltage should vary at least eight times in ten seconds between 0.2 and 0.8 volts (normal range).
- Drive system rich: The use of a properly adjusted propane flow-meter (J-26911) is industry standard.
Voltage should increase to at least 0.8 volts within two to three seconds.
- Drive system lean: Create a vacuum leak from a source that is not an control module input or output.
Voltage should drop to at least 0.3 volts within two to three seconds.
NOTE After each test the O2 sensor should return to normal operating range within two to three seconds.
- O2 Sensor should be replaced for failure to pass any of the tests above.
NOTE A CEC system that is operating excessively rich or lean will drive the 02 sensor to its maximum range and should be repaired first and not diagnosed as a 02 sensor failure.
- Reconnect all hoses and electrical connectors. Clear all codes set and retrain idle.
HEATING ELEMENT (H20S only)
- Turn ignition "OFF". Disconnect electrical connector.
- Connect test light between harness terminals "A" and "B".
- Turn ignition "ON". Test light should be "ON".
- If test light is "OFF", connect test light to harness terminal "A" to ground. Light should be "ON" ensuring power circuit is operating correctly.
- Turn ignition "OFF".
- Using an ohmmeter, measure resistance between terminals A and B.
Resistance @ Specified Temperature
3.5 ohms @ 20°C (68°F)
14 ohms @ 350°C (662°F)
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.