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.
1989 Geo Metro BaseFACTORY OEM SERVICE PROCEDURE
Oxygen Sensor
- Start engine and warm to operating temperature. Pull back connector seal at oxygen sensor. Using a digital voltmeter with at least a 10-megohm input impedance, backprobe oxygen sensor connector. If connector is inaccessible, backprobe control unit at appropriate terminal. See appropriate L - WIRING DIAGRAM in this section.
- With engine at idle, remove a large vacuum hose from intake manifold to create a large vacuum leak (without causing engine to stall). Voltage reading at oxygen sensor should drop. Reconnect vacuum line and voltage at voltmeter should increase. If voltage readings do not respond as specified, replace oxygen sensor.
Factory Service Tools
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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.