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. 40) from the output terminal (terminal No. 4) of the left bank heated oxygen sensor (rear).
Terminal No. 2 of the left bank heated oxygen sensor (rear) is grounded with ECM (terminal No. 41).
The ECM applies an offset voltage of 0.5 volt to terminal No. 2 of the left bank heated oxygen sensor (rear).
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 check for the left bank heated oxygen sensor (rear) output voltage.
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 23. OBD-II Drive Cycle
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
Left bank heated oxygen sensor (rear) failed.
Connector damage.
Harness damage.
ECM failed.
DIAGNOSIS
Required Special Tools:
- MB991316: Test Harness
STEP 1. Check harness connector B-13 at the left bank heated oxygen sensor (rear) 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 (rear).
1. Disconnect the left bank heated oxygen sensor (rear) connector B-13 and connect test harness special tool, MD991316 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. 1 (red clip) and terminal No. 3 (blue clip).
5. Measure the output voltage of heated oxygen sensor under the following driving.
a. Transaxle: 2nd speed
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 measured resistance between 11 and 18 ohms [at 20 °C (68 °F)?
YES: Go to Step 3.
NO: Replace the left bank heated oxygen sensor (rear). Then go to Step 5.
STEP 3. Check for harness between the left bank heated oxygen sensor (rear) connector B-13 and ECM connector B-10.
1. Disconnect the left bank heated oxygen sensor (rear) connector B-13 and the ECM connector B-10.
2. Measure the resistance between the heated oxygen sensor connector B-13 and the ECM connector B-10.
a. Connector B-13 (terminal No. 2) and connector B-10 (terminal No. 41).
b. Connector B-13 (terminal No. 4) and connector B-10 (terminal No. 40).
Should be less than 2 ohms.
3. Check for the continuity between the oxygen sensor connector B-14 and ground.
a. Connector B-13 (terminal No. 2) and ground
b. Connector B-13 (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. Check the trouble symptoms.
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 P0157 set?
YES: Replace the ECM. When the ECM is replaced, register the ID code. Refer to, ID Code Registration Judgment Table
NO: It can be assumed that this malfunction is intermittent.
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 P0157 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.