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 MANUALSSUBARU1994LEGACY L, 4D SEDAN, FWD, STANDARDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - TESTS W/CODESDIAGNOSTIC CODE TESTINGCODE 23 - AIRFLOW SENSOR
1994 Subaru Legacy L, 4D Sedan, FWD, Standard
Code 23 - Airflow Sensor
1994 Subaru Legacy L, 4D Sedan, FWD, StandardSECTION Code 23 - Airflow Sensor
NOTE:
Refer to illustration for ECU connector and terminal identification. See Figure
.
- Turn ignition on. Ensure ECU is connected. Measure voltage between ECU connector B48, terminal No. 8 (backprobe) and ground. With engine off, 10-13 volts should be present. With engine at idle, 13-14 volts should be present.
- Measure voltage between ECU connector B48, terminal No. 9 (backprobe) and ground. With engine off, 0-.3 volt should be present. With engine at idle, .8-1.2 volts should be present.
- Measure voltage between ECU connector B48, terminal No. 10 (backprobe) and ground. With engine off or at idle, no voltage should be present. If voltages are to specification, check ECU terminals for poor contact or replace ECU. If voltages are not to specification, go to next step.
- Turn ignition off. Disconnect ECU and airflow sensor connectors. Measure resistance between ECU connector B48, terminal No. 8 and airflow sensor terminal No. 1 (Red wire), between ECU connector B48, terminal No. 9 and airflow sensor terminal No. 4, and between ECU connector B48, terminal No. 10 and airflow sensor terminal No. 2. Zero ohms should be present in all cases. If zero ohms is not present, repair harness or connector(s).
- Measure resistance between airflow sensor connector terminals and ground. See AIRFLOW SENSOR CONNECTOR TERMINAL/GROUND RESISTANCE table. If resistances are within specification, replace airflow sensor. If resistances are not within specification, repair airflow sensor harness connector.
AIRFLOW SENSOR CONNECTOR TERMINAL/GROUND RESISTANCE
| Airflow Sensor Terminal (Wire Color) | Ohms |
|---|---|
| No. 1 (Red Wire) | Minimum One Megohm |
| No. 4 (Black Wire) | Minimum One Megohm |
| No. 2 (White Wire) | Minimum One Megohm |
| No. 3 (Black/Red Wire) | Zero |
RENDER: 1.0x
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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.