P0157
DTC P0157: Heated Oxygen Sensor Circuit Low Voltage (bank 2, sensor 2)Left Bank Heated Oxygen Sensor (rear) Circuit Part 1:
Left Bank Heated Oxygen Sensor (rear) Circuit Part 2:
CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM
- Terminal No. 2 of the left bank heated oxygen sensor (rear) is grounded with ECM
- The ECM
TECHNICAL DESCRIPTION
- The output signal of the left bank heated oxygen sensor (front) is compensated by the output signal of the left bank heated oxygen sensor (rear).
- The ECM
DESCRIPTIONS OF MONITOR METHODS
Left bank heated oxygen sensor (rear) out put voltage is under the 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
- Heated oxygen sensor heater (rear) monitor
- Air/fuel ratio feedback monitor
Sensor (The sensor below is determined to be normal)
- Mass airflow sensor
- Engine coolant temperature sensor
- Intake air temperature sensor
- Barometric pressure 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.
- 3 minutes or more have passed since the engine starting sequence was completed.
Judgement Criterion
- Left bank heated oxygen sensor output voltage is lower than 0.2 volt for 2 seconds.
OBD-II Drive Cycle PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 21. OBD-II Drive Cycle
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Left bank heated oxygen sensor (rear) failed.
- Open or shorted circuit in left bank heated oxygen sensor (rear) output line, or harness damage.
- Open circuit in left bank heated oxygen sensor (rear) ground line, or harness damage.
- Connector damage.
- ECM failed.
- PCM failed.
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
- MB991923: Power Plant ECU Check Harness
STEP 1. Using scan tool MB991958, check data list item AF: Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).
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 AF, Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).
a. Transaxle: 2nd speed (A/T: "L" range)
b. Drive with wide open throttle
c. Engine: 3,500 r/min
- The output voltages should be between 0.6 and 1.0 volt.
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 How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.
NO: Go to Step 2.
STEP 2. Measure the sensor output voltage at left bank heated oxygen sensor (rear) connector B-23 by backprobing.
1. Do not disconnect the connector B-23.
2. Start the engine and run at idle.
3. Measure the voltage between terminal No. 4 and ground by backprobing under the following driving.
a. Transaxle: 2nd speed (A/T: "L" range)
b. Drive with wide open throttle
c. Engine: 3,500 r/min or more
- The output voltage should be between 1.0 and 1.5 volts.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 1.0 and 1.5 volts?
YES: Go to Step 3.
NO: Go to Step 7.
STEP 3. Measure the sensor output voltage at ECM
1. Disconnect all ECM
2. Start the engine and run at idle.
3. Measure the voltage between terminal No. 96 and ground by backprobing under the following driving.
a. Transaxle: 2nd speed (A/T: "L" range)
b. Drive with wide open throttle
c. Engine: 3,500 r/min or more
- The output voltage should be between 1.0 and 1.5 volts.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 1.0 and 1.5 volts?
YES: Go to Step 4.
NO: Go to Step 6.
STEP 4. Check harness connector B-23 at left bank heated oxygen sensor (rear) and harness connector B-21 at ECM
Q: Is the harness connector in good condition?
YES: Go to Step 5.
NO: Repair or replace it. Then go to Step 14.
STEP 5. Using scan tool MB991958, check data list item AF: Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).
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 AF, Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).
a. Transaxle: 2nd speed (A/T: "L" range)
b. Drive with wide open throttle
c. Engine: 3,500 r/min
- The output voltages should be between 0.6 and 1.0 volt.
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 How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.
NO: Replace the ECM or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Then go to Step 14.
STEP 6. Check harness connector B-23 at left bank heated oxygen sensor (rear) and harness connector B-21 at ECM
Q: Is the harness connector in good condition?
YES: Repair harness wire between left bank heated oxygen sensor (rear) connector B-23 (terminal No. 4) and ECM
NO: Repair or replace it. Then go to Step 14
STEP 7. Check harness connector B-23 at left bank heated oxygen sensor (rear) for damage.
Q: Is the harness connector in good condition?
YES: Go to Step 8.
NO: Repair or replace it. Then go to Step 14.
STEP 8. Measure the sensor offset voltage at ECM
1. Disconnect all ECM
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 105 and ground.
- Voltage should be between 0.4 and 0.6 volt.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the measured voltage between 0.4 and 0.6 volt?
YES: Go to Step 10.
NO: Go to Step 9.
STEP 9. Check harness connector B-21 at ECM
Q: Is the harness connector in good condition?
YES: Repair harness wire between left bank heated oxygen sensor (rear) connector B-24 (terminal No. 2) and ECM
NO: Repair or replace it. Then go to Step 14.
STEP 10. Check harness connector B-21 at ECM
Q: Is the harness connector in good condition?
YES: Go to Step 11.
NO: Repair or replace it. Then go to Step 14.
STEP 11. Check for harness damage between left bank heated oxygen sensor (rear) connector B-23 (terminal No. 2) and ECM
Q: Is the harness wire in good condition?
YES: Go to Step 12.
NO: Repair it. Then go to Step 14.
STEP 12. Check for short circuit to ground and harness damage between left bank heated oxygen sensor (rear) connector B-23 (terminal No. 4) and ECM
Q: Is the harness wire in good condition?
YES: Go to Step 13.
NO: Repair it. Then go to Step 14.
STEP 13. Check the left bank heated oxygen sensor (rear).
1. Disconnect the left bank heated oxygen sensor (rear) connector B-23 and connect test harness special tool, MB991316, to the connector on the left bank heated oxygen sensor (rear) side.
2. Warm up the engine until engine coolant temperature reaches 80 °C (176 °F) or higher.
3. Drive at 50 km/h (31 mph) or more for 10 minutes.
4. Connect a digital voltage meter between terminal No. 2 (black clip) and terminal No. 4 (white clip).
5. Measure the output voltage of heated oxygen sensor under the following driving.
a. Transaxle: 2nd speed (A/T: "L" range)
b. Drive with wide open throttle
c. Engine: 3,500 r/min or more
Standard value: 0.6 - 1.0 volts
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.
Q: Is the voltage between 0.6 and 1.0 volts?
YES: Replace the ECM or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Then go to Step 14.
NO: Replace the left bank heated oxygen sensor (rear). Then go to Step 14.
STEP 14. 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 21. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0157 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.