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 MANUALSVOLVO1991940 TURBO, 4D SEDAN, AW71REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - SYSTEM/COMPONENT TESTSFUEL SYSTEMFUEL CONTROLOXYGEN (O2) SENSOR CURRENT FEED & HEATER RESISTANCE
1991 Volvo 940 Turbo, 4D Sedan, AW71
Oxygen (O2) Sensor Current Feed & Heater Resistance
1991 Volvo 940 Turbo, 4D Sedan, AW71SECTION Oxygen (O2) Sensor Current Feed & Heater Resistance
- Connect voltmeter between ground and terminal No. 1 of 2-wire connector located next to firewall. Voltage reading should be battery voltage. Remove ground wire from fuel injection ECU terminal No. 20.
- Connect ohmmeter between oxygen sensor harness terminal No. 2 (Black wire) and ground. Connector is located next to firewall. With a cold oxygen sensor, resistance should be 2-3 ohms. With a oxygen sensor warmer than 660°F (350°C), resistance should be 7-14 ohms. Replace oxygen sensor as necessary.
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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.