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.
Test Step 4 - O2 Sensor Test
- Turn the ignition off.
Check for contaminants that may cause improper O2 sensor operation, such as contaminated fuel, unapproved silicone, or evidence of oil or coolant.
- Disconnect the O2 sensor harness connector.
- Turn the ignition on.
- With a scan tool, monitor the O2 sensor voltage.
The voltage should be approximately 5.0 volts with the connector disconnected.
- Connect a jumper wire between the signal circuit and the return circuit in the O2 sensor harness connector.
The voltage should drop from 5.0 volts to 2.5 volts with the jumper wire in place.
Is the O2 sensor voltage displayed on the scan tool as described?
Yes
- Replace the O2 sensor. Refer to FOR ENGINE CJRA - REMOVAL AND INSTALLATION , FOR ENGINE CGVA - REMOVAL AND INSTALLATION or FOR ENGINE CGUA - REMOVAL AND INSTALLATION .
- Perform the PCM Verification Test. Refer to PCM VERIFICATION TEST .
No
- Go to Test Step TEST STEP 5 - O2 SENSOR SIGNAL CIRCUIT .
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.