P0157
DTC P0157: Heated Oxygen Sensor Circuit Low Voltage (bank 2, sensor 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 (front) monitor
- Heated oxygen sensor (rear) heater monitor
- Heated oxygen sensor (front) heater monitor
- Heated oxygen sensor (front) inactive monitor
- Heated oxygen sensor offset voltage 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
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 (rear) 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 Monitors, Trips, Drive Cycles and Readiness Codes.
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. Harness Connector Inspection.
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. 2 (black clip) and terminal No. 4
(white clip).
(5)Measure the output voltage of heated oxygen sensor under the following driving.
1. Transaxle: 2nd speed
2. Drive with wide open throttle
3. Engine: 3,500 r/min or more
Standard value: 0.6 - 1.0 volts
NOTE:
If the temperature of sensing area does not reach the high temperature [of approximately 400°C (752°F) or more] even though the oxygen sensor is normal, the output voltage would be possibly low in spite of the rich air-fuel ratio.
NOTE:
When the vehicle is driven with high loads, the temperature of the sensing area of the heated oxygen sensor is sufficiently high. Thus, it is not necessary to apply the voltage to the heater.
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.
(3) 4. Connector B-13 (terminal No. 2) and connector B-10 (terminal No. 41).
5. Connector B-13 (terminal No. 4) and connector B-10 (terminal No. 40).
- Should be less than 2 ohms.
(4)Check for the continuity between the oxygen sensor connector B-13 and ground.
6. Connector B-13 (terminal No. 2) and ground
7. 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. Harness Connector Inspection.
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 21 Monitors, Trips, Drive Cycles and Readiness Codes
(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 registration procedure manual - ID codes registration judgement table [Vehicles with KOS] or ID registration procedure manual - ID codes registration judgement table [Vehicles with WCM]. Then go to Step 5.
NO It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.
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 21 Monitors, Trips, Drive Cycles and Readiness Codes.
(2)Check the diagnostic trouble code (DTC).
Q. Is DTC P0157 set?
YES Retry the troubleshooting.
NO The inspection is complete.