Some 3S-GE, 3S-GTE and 4A-FE engines, especially California engines, use a heated oxygen sensor. This allows the sensor to start functioning sooner in a cold engine. To test, use an ohmmeter and measure the resistance between terminals +B and HT. If the resistance is not 5.1-6.3 kilo-ohms at 68° F (20° C), replace the sensor.
If fuel mileage is suffering or engine performance is not quite as it used to be, follow the oxygen sensor testing procedure found in the diagnostic charts in this section.Sub-Oxygen Sensor
The 3S-FE and 5S-FE engines in California use this sensor. It should be checked only when Code 27 is displayed.
- Clear the diagnostic code memory.
- Warm up the engine to normal operating temperature.
- Drive for 5 minutes between 50-55 mph in 4th or 5th gear (MT) or in Drive (AT).
- Following the procedures in step 3, press fully on the accelerator pedal for 2 seconds. Do NOT exceed 62 mph or the diagnostic code will be canceled.
- Stop the vehicle and turn off the engine.
- Repeat steps 2 and 3.
- If Code 27 reappears, check the sub-oxygen sensor circuit or replace the sensor.
REMOVAL & INSTALLATION
- Disconnect the negative battery cable.
- Unplug the electrical wiring connector leading from the O 2 sensor.
- Unscrew the two nuts and carefully pull out the sensor.
- Installation is in the reverse order of removal procedure. Always use a new mounting gasket. Tighten the nuts to 13-16 ft. lbs. (18-24 Nm).