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 Lexus SC 300 AutomaticFACTORY OEM SERVICE PROCEDURE
ACIS Circuit
- Check ACIS Vacuum Switching Valve (VSV). See Figure. See ACIS VACUUM SWITCHING VALVE (VSV) . If VSV is okay, pull back the right front floor mat. Remove ECM protective cover. Connect a Check Harness (09990-01000) between ECM and harness. See USING CHECK HARNESS under INTRODUCTION. Turn ignition on.
- Measure voltage between chassis ground and terminal No. 39 of ECM connector "B" (Green/Red wire). To identify ECM connectors and terminals, see Figure.
- If battery voltage is present, check for faulty vacuum tank or hoses. See ACIS VACUUM TANK . If battery voltage is not present, check for open or shorted circuit between EFI main relay and ECM. If circuit is okay, replace ECM.
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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