P0133

DTC P0133: Cylinder 1, 4 Heated Oxygen Sensor (front) Circuit Slow Response














CIRCUIT OPERATION

- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM[ M/T] or the PCM[ A/T] (terminal No. 92) from the output terminal (terminal No. 4) of the cylinder 1, 4 heated oxygen sensor (front).
- Terminal No. 2 of the cylinder 1, 4 heated oxygen sensor (front) is grounded with ECM[ M/T] or PCM[ A/T] (terminal No. 80).
- The ECM[ M/T] or the PCM[ A/T] applies an offset voltage of 0.5 volt to terminal No. 2 of the cylinder 1, 4 heated oxygen sensor (front).

TECHNICAL DESCRIPTION

- The cylinder 1, 4 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[ M/T] or the PCM[ A/T].
- When the cylinder 1, 4 heated oxygen sensor (front) begins to deteriorate, the heated oxygen sensor signal response becomes poor.
- The ECM[ M/T] or the PCM[ A/T] checks for the cylinder 1, 4 heated oxygen sensor (front) rich/lean switching frequency.

DESCRIPTIONS OF MONITOR METHODS

Cylinder 1, 4 heated oxygen sensor (front) rich/lean switching frequency is under specified value.

MONITOR EXECUTION

Continuous

MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored in memory for the item monitored below)

- Heated oxygen sensor heater (front) monitor
- Misfire monitor
- Fuel system monitor
Sensor (The sensor below is determined to be normal)

- Mass airflow sensor
- Engine coolant temperature sensor
- Intake air temperature sensor
- Barometric pressure sensor
- Throttle position sensor
- Accelerator pedal position sensor

DTC SET CONDITIONS

Logic Flow Chart






Check Conditions

- Engine coolant temperature is higher than 60°C (140°F).
- Engine speed is between 1,500 and 3,500 r/min[ M/T] or 1,200 and 3,500 r/min[ A/T].
- Volumetric efficiency is between 18 and 70 percent[ M/T] or 25 and 70 percent[ A/T].
- Under the closed loop air/fuel control.
- The accelerator pedal is depressed.
- Short-term fuel trim is between -25 and +25 percent.
- More than 2 seconds have elapsed after the above mentioned conditions have been met.
- During the drive cycle, the ECM[ M/T] or the PCM[ A/T] performs monitoring with the accumulated total time of 10 seconds, 5 times.
Judgement Criteria

- The average of the cylinder 1, 4 heated oxygen sensor (front) rich/lean switching frequency is less than 12 times for the accumulated time of 10 seconds.

- The cylinder 1, 4 heated oxygen sensor (front) rich/lean switching frequency is less than 25 times for the accumulated time of 10 seconds.

NOTE:
If the sensor switching frequency is lower than the Judgement Criteria due to the M.U.T.-III 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 second.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 Monitors, Trips, Drive Cycles and Readiness Codes .

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)

- Cylinder 1, 4 heated oxygen sensor (front) deteriorated.
- Connector damage.
- ECM failed.[ M/T]
- PCM failed.[ A/T]

DIAGNOSIS

Required Special Tools:

- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
- MB991316: Test Harness

STEP 1. Using scan tool MB991958, check data list item AC: Cylinder 1, 4 Heated Oxygen Sensor (front).





CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK"
(OFF) position before connecting or disconnecting scan tool MB991958.

(1)Connect scan tool MB991958 to the data link connector.
(2)Start the engine and run at idle.
(3)Set scan tool MB991958 to the data reading mode for item AC, Cylinder 1, 4 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. How to Cope With Intermittent Malfunctions.

NO Go to Step 2.

STEP 2. Check the cylinder 1, 4 heated oxygen sensor (front).





(1)Disconnect the cylinder 1, 4 heated oxygen sensor (front) connector B-36 and connect test harness special tool MB991316 to the connector on the cylinder 1, 4 heated oxygen sensor (front) side.
(2)Warm up the engine until engine coolant temperature reaches 80°C (176°F) or higher.
(3)Rev the engine for 5 minutes or more with the engine speed of 2,500 r/min.





(4)Connect a digital voltage meter between terminal No. 2 (black clip) and terminal No. 4
(white clip).
(5)Warm up the engine, 2,500 r/min

- Output voltage repeats 0 - 0.4 volt and 0.6 - 1.0 volt 10 times or more within 10 seconds.

CAUTION:

- Be very careful when connecting the jumper wires; incorrect connection can damage the heated oxygen sensor.
- Be careful the heater is broken when voltage of beyond 8 volts is applied to the heated oxygen sensor heater.

NOTE:
If the temperature of sensing area does not reach the high temperature [of approximately 400°C (752°F) or more] even through the heated oxygen sensor is normal, the output voltage would be possibly low in spite of the rich air-fuel ratio. Therefore, if the output voltage is low, use a jumper wire to connect the terminal No. 1 (red clip) and the terminal No. 3 (blue clip) of the heated oxygen sensor with the positive terminal and the negative terminal of 8 volts power supply respectively, then check again.

Q. Is the sensor operating properly?

YES Go to Step 3.

NO Replace the cylinder 1, 4 heated oxygen sensor (front). Then go to Step 4.

STEP 3. Check harness connector B-36 at cylinder 1, 4 heated oxygen sensor (front) and harness connector B-20, B-21 at ECM [M/T] or PCM [A/T] for damage.









Q. Is the harness connector in good condition?

YES Replace the ECM or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Encrypted Code Registration Criteria Table.
Then go to Step 4.

NO Repair or replace it. Harness Connector Inspection.
Then go to Step 4.

STEP 4. Test the OBD-II drive cycle.

(1)Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 Monitors, Trips, Drive Cycles and Readiness Codes.

(2)Check the diagnostic trouble code (DTC).

Q. Is DTC P0133 set?

YES Retry the troubleshooting.
NO The inspection is complete.