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.
1994 Subaru Loyale AutomaticFACTORY OEM SERVICE PROCEDURE
By-Pass Air Control Valve
- With engine running, unplug electrical connector from by-pass air control valve. By-pass air control valve is located near throttle body. Engine speed should drop slightly with engine warm, and significantly with engine cold. Reconnect wiring. Engine speed should return to previous value.
- If engine speed does not return to previous value, turn engine off. Turn ignition on. Check for battery voltage at Black/White wire of Air Control Valve (ACV) electrical connector. See WIRING DIAGRAMS article.
- Turn ignition off. Measure resistance between ACV terminals. If resistance is not 7.3-13.0 ohms, replace ACV. Check ACV solenoid for short to ground. If short exists, replace ACV.
- Reconnect wiring to ACV. Unplug connector at ECU. Turn ignition on. Check for battery voltage at terminal C45 (Green/Red wire) of ECU connector. If voltage is not as specified, check harness between ACV and ECU.
- Turn ignition off. Reconnect wiring to ECU. Turn ignition on. Backprobe terminal C45 (Green/Red wire) of ECU. Voltage should be one volt or less for about one minute after ignition is turned on. After one minute, voltage should be at least 10 volts. If voltage is not as specified, check for a bad ground, problem with ECU circuits (sensors) or faulty ECU.
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.
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