P0133

Heated Oxygen Sensor (front) Circuit:

Connector: C-105:

CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal 76) or PCM (terminal 71) from the output terminal (terminal 4) of the heated oxygen sensor (front).
- Terminal 2 of the heated oxygen sensor (front) is grounded with ECM (terminal 92) or PCM (terminal 57) .

TECHNICAL DESCRIPTION
- The heated oxygen sensor (front) detects the concentration of oxygen in the exhaust gas; it converts those data to voltage, and inputs the resulting signals to the ECM or PCM .
- When the heated oxygen sensor (front) begins to deteriorate, the heated oxygen sensor signal response becomes poor.
- The ECM or PCM forcibly varies the air/fuel mixture to make it leaner and richer, and checks the response speed of the heated oxygen sensor (front). In addition, the ECM or PCM also checks for an open circuit in the heated oxygen sensor (front) output line.

DTC SET CONDITIONS

Check Conditions
- Engine coolant temperature is higher than 50 °C (122 °F).
- Engine speed is at between 1,200 and 3,000 r/min.
- Volumetric efficiency is at between 20 and 60 percent.
- Under the closed loop air/fuel control.
- Short-term fuel trim is at between -25 and +25 percent.
- The throttle valve is open.
- More than 2 seconds have elapsed after the above mentioned conditions have been met.
- Monitoring time: 10 seconds x 5 times.

Judgment Criteria
- The heated oxygen sensor (front) sends "lean" and "rich" signals alternately 10 times or less for 10 seconds.

NOTE: If the sensor switching frequency is lower than the Judgment Criteria due to the MUT-II OBD-II test Mode - HO2S Test Results, it is assumed that the heated oxygen sensor has deteriorated. If it is higher, it is assumed that the harness is damaged or has a short circuit.
If the heated oxygen sensor signal voltage has not changed even once (lean/rich) after the DTC was erased, the sensor switch time will display as 0 seconds.

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Heated oxygen sensor (front) deteriorated.
- ECM failed.
- PCM failed.

DIAGNOSIS

Required Special Tools
- MB991502: Scan Tool (MUT-II)

STEP 1. Using scan tool MB991502, check data list item 11: Heated Oxygen Sensor (front).

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.

1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 11, Heated Oxygen Sensor (front).
4. Warm up the engine, 2,500 r/min.
- Output voltage repeats 0.4 volt or less and 0.6 - 1.0 volt 10 times or more within 10 seconds.

5. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the sensor operating properly?

YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points.

NO: Replace the heated oxygen sensor (front). Then go to Step 2.

STEP 2. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to, Procedure 4 - Heated Oxygen Sensor Monitor.
2. Check the diagnostic trouble code (DTC).

Q: Is the DTC P0133 output?

YES: Retry the troubleshooting.

NO: The inspection is complete.