P0131
Right Bank Heated Oxygen Sensor (front) Circuit:
Connectors:
DTC P0131: Heated Oxygen Sensor Circuit Low Voltage (bank 1, sensor 1)
CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal No. 72)
- Terminal No. 2 of the right bank heated oxygen sensor (front) is grounded with ECM (terminal No. 49)
TECHNICAL DESCRIPTION
- The right bank 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
- When the right bank heated oxygen sensor (front) begins to deteriorate, the heated oxygen sensor signal response becomes poor.
- The ECM
DESCRIPTIONS OF MONITOR METHODS
Right bank heated oxygen sensor (front) output voltage stays low when air/fuel ratio is forced to be rich. The above procedure is repeated when oxygen sensor is inactive.
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)
- Volume airflow sensor
- Engine coolant temperature sensor
- Intake air temperature sensor
- Barometric pressure sensor
- Throttle position sensor
DTC SET CONDITIONS
Logic Flow Chart:
Check Conditions
- After 2 seconds or more pass from the time when the monitor determines normally for detecting an open circuit.
- Right bank heated oxygen sensor (front) signal voltage has continued to be 0.2 volt or lower.
- Engine coolant temperature is higher than 76° C (169° F).
- Volume airflow sensor output frequency is 75 Hz or more.
- At least 20 seconds have passed since fuel shut off control was canceled.
- Monitoring time: 8 seconds.
Judgement Criteria
- Making the air/fuel ratio 15 percent for 8 seconds richer does not result in raising the heated oxygen sensor (front) output voltage beyond 0.2 volt.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 6 - Other Monitor.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are: )
- Right bank heated oxygen sensor (front) failed.
- Short circuit in right bank heated oxygen sensor (front) output line.
- ECM failed.
- PCM failed.
- Connector damage.
DIAGNOSIS
Required Special Tools:
- MB991502: Scan Tool (MUT-II)
- MD998464: Test Harness
STEP 1. Using scan tool MB991502, check data list item 39: Heated Oxygen Sensor Bank 1, Sensor 1 (right 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 39, Heated Oxygen Sensor Bank 1, Sensor 1 (right front).
- Warming up the engine. When the engine is revved, the output voltage should be 0.6 to 1.0 volt.
- Warming up the engine. When the engine is idling, the output voltage should repeat 0.4 volt and 0.6 to 1.0 volt alternately.
4. 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 INTRODUCTION, How to Use Troubleshooting/Inspection Service Points How to Cope with Intermittent Malfunctions.
NO: Go to Step 2.
STEP 2. Check the right bank heated oxygen sensor (front).
1. Disconnect the right bank heated oxygen sensor (front) connector B-27 and connect test harness special tool, MD998464, to the connector on the right bank heated oxygen sensor (front) side.
2. Warm up the engine until engine coolant temperature reaches 80° C (176° F) or higher.
3. Perform a racing for 5 minutes or more with the engine speed of 4,500 r/min.
4. Connect a digital voltage meter between terminal No. 2 (black clip) and terminal No. 4 (white clip).
5. While repeatedly revving the engine, measure the right bank heated oxygen sensor (front) output voltage.
Standard value: 0.6 - 1.0 volt
CAUTION:
- Be very careful when connecting the jumper wires; incorrect connection can damage the right bank heated oxygen sensor.
- Be careful the heater is broken when voltage of beyond 8 volts is applied to the right bank heated oxygen sensor heater.
NOTE: If the sufficiently high temperature [of approximate 400° C (752° F) or more] is not reached although the right bank heated oxygen sensor is normal, the output voltage would be possibly low although 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 right bank heated oxygen sensor with the positive terminal and the negative terminal of 8 volts power supply respectively, then check again.
Q: Is the measured voltage between 0.6 and 1.0 volt?
YES: Go to Step 3.
NO: Replace the right bank heated oxygen sensor (front). Then go to Step 5.
STEP 3. Check connector B-27 at right bank heated oxygen sensor (front) and connector C-122 at ECM
Q: Is the connector in good condition?
YES: Go to Step 4.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 5.
STEP 4. Check for short circuit to ground between right bank heated oxygen sensor (front) connector B-27 (terminal No. 4) and ECM connector C-122 (terminal No. 72)
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 5.
NO: Repair it. Then go to Step 5.
STEP 5. 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 - Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0131 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.