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 MANUALSBUICK1990SKYLARK BASE, 4D SEDAN, 125C/MD9REPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - 2.5L TBIDIAGNOSTIC CODESCODE 13, OPEN OXYGEN SENSOR CIRCUITNOTES
1990 Buick Skylark Base, 4D Sedan, 125C/MD9
Code 13, Open Oxygen Sensor Circuit: Notes
1990 Buick Skylark Base, 4D Sedan, 125C/MD9SECTION Notes
The O2 sensor is like an open circuit and produces no voltage when its temperature is less than about 600°F (316°C). An open sensor circuit or cold sensor causes "open loop" operation.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- Code 13 will set at normal operating temperature if at least 2 minutes have passed since engine start, O2 signal voltage is steady between .35-.55 volt and throttle position sensor signal is greater than 7 percent (1200 RPM). All conditions must be met for a precalibrated period of time.
- This test determines if the O2 sensor, ECM or wiring is at fault.
- Use only a high-impedance DVOM for this test. This checks for continuity in signal and ground circuits. If ground circuit is open, voltage on signal circuit will be greater than .6 volt.
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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.