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.
1993 Lexus SC 300 AutomaticFACTORY OEM SERVICE PROCEDURE
Code 27 (Calif.)
Condition is one of the following:
- Open or short in heater circuit of sub-heated oxygen sensor for more than 0.5 second. Probable cause: open or short in heater circuit of sub-heated oxygen sensor, defective sub -heated oxygen sensor or defective oxygen sensor.
- Main oxygen sensor signal is more than 0.5 volt and sub -oxygen sensor signal is less than 0.5 volt with engine temperature more than 176°F (80°C), engine speed more than 1500 RPM and accelerator pedal fully depressed for 2 seconds. Probable cause: open or short in heater circuit of sub-heated oxygen sensor, defective sub-heated oxygen sensor or defective 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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