P0151
DTC P0151: Heated Oxygen Sensor Circuit Low Voltage (bank 2, sensor 1)Left Bank Heated Oxygen Sensor (front) Circuit Part 1:
Left Bank Heated Oxygen Sensor (front) Circuit Part 2:
CIRCUIT OPERATION
A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal No. 38) from the output terminal (terminal No. 4) of the left bank heated oxygen sensor (front).
Terminal No. 2 of the left bank heated oxygen sensor (front) is grounded with or ECM (terminal No. 39).
The ECM applies an offset voltage of 0.5 volt to terminal No. 2 of the left bank heated oxygen sensor (front).
TECHNICAL DESCRIPTION
The left bank heated oxygen sensor (front) detects the concentration of oxygen in the exhaust gas; it converts that data to voltage, and sends it to the ECM.
When the left bank heated oxygen sensor (front) begins to deteriorate, the heated oxygen sensor signal response deteriorates also.
The ECM also checks for the left bank heated oxygen sensor (front) output voltage.
DESCRIPTIONS OF MONITOR METHODS
The left bank heated oxygen sensor (front) output voltage is under specified range.
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:
Logic Flow Chart
Check Conditions
Heated oxygen sensor offset voltage is between 0.4 and 0.6 volt.
Battery positive voltage is between 11 and 16.5 volts.
Typically 60 seconds have passed since the engine starting sequence was completed.
Judgement Criterion
Left bank heated oxygen sensor (front) output voltage is lower than 0.2 volts.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 23. OBD-II Drive Cycle
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
Left bank heated oxygen sensor (front) failed.
Connector damage.
Harness damage.
ECM failed.
DIAGNOSIS
STEP 1. Check harness connector B-14 at the left bank heated oxygen sensor (front) and harness connector B-10 at the ECM for damage.
Q: Is the harness connector in good condition?
YES: Go to Step 2.
NO: Repair or replace it. Then go to Step 5.
STEP 2. Check the left bank heated oxygen sensor (front).
1. Disconnect the left bank heated oxygen sensor (front) connector B-14 and connect test harness special tool, MB998464, to the connector on the left bank 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. While repeatedly revving the engine, measure the right bank heated oxygen sensor (front) output voltage.
Standard value: 0.6 - 1.0 volts
CAUTION:
- Be very careful when connecting the jumper wires; incorrect connection can damage the heated oxygen sensor.
- Be careful the heater can be damaged if a voltage beyond 8 volts is applied to the heated oxygen sensor heater.
NOTE: If the sufficiently high temperature [of approximate 400 °C (752 °F) or more] is not reached although the 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 heated oxygen sensor with the positive terminal and the negative terminal of 8 volts power supply respectively, then check again.
Q: Is the voltage between 0.6 and 1.0 volts?
YES: Go to Step 3.
NO: Replace the left bank heated oxygen sensor (front). Then go to Step 5.
STEP 3. Check for harness between the left heated oxygen sensor (front) connector B-14 and the ECM connector B-10.
1. Disconnect the left bank heated oxygen sensor (front) connector B-14 and the ECM connector B-10.
2. Measure the resistance between the heated oxygen sensor connector B-14 and the ECM connector B-10.
a. Connector B-14 (terminal No. 2) and connector B-10 (terminal No. 39).
b. Connector B-14 (terminal No. 4) and connector B-10 (terminal No. 38).
Should be less than 2 ohms.
3. Check for the continuity between the oxygen sensor connector B-14 and ground.
a. Connector B-14 (terminal No. 2) and ground
b. Connector B-14 (terminal No. 4) and ground
Not continuity.
Q: Is the harness wire in good condition?
YES: Go to Step 4.
NO: Repair it. Then go to Step 5.
STEP 4. Using scan tool MB991958, check data list item AE: Heated Oxygen Sensor Bank 2, Sensor 1 (left 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 AE, Heated Oxygen Sensor Bank 2, Sensor 1 (left front).
Warm up the engine. When the engine is revved, the output voltage should battery positive voltage.
Warm up the engine. When the engine is idling, the output voltage should repeat 0.4 volt or less 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.
NO: Replace the ECM. 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 - Pattern 23. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0151 set?
YES: Retry the troubleshooting.
NO: It can be assumed that this malfunction is intermittent.