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 [M/T] or the PCM [A/T] (terminal No. 96) 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 [M/T] or PCM [A/T] (terminal No. 105).
- The ECM [M/T] or the PCM [A/T] 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 [M/T] or the PCM [A/T] 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






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 22 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. [M/T]
- PCM failed. [A/T]

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).
1. Transaxle: 2nd speed

2. Drive with wide open throttle

3. 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. 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.
4. Transaxle: 2nd speed

5. Drive with wide open throttle

6. 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 [M/T] or PCM [A/T] connector B-21 by using power plant ECU check harness special tool MB991923.









(1)Disconnect all ECM [M/T] connectors or PCM [A/T] connectors. Connect the power plant ECU check harness special tool MB991923 between the separated connectors.
(2)Start the engine and run at idle.





(3)Measure the voltage between terminal No. 96 and ground by backprobing under the following driving.
7. Transaxle: 2nd speed

8. Drive with wide open throttle

9. 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 [M/T] or PCM [A/T] for damage.









Q. Is the harness connector in good condition?

YES Go to Step 5.

NO Repair or replace it. Harness Connector Inspection.
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).
10. Transaxle: 2nd speed

11. Drive with wide open throttle

12. 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. 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. Immobilizer System.
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 [M/T] or PCM [A/T] for damage.









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 [M/T] or PCM [A/T] connector B-21 (terminal No. 96) because of open circuit or harness damage. Then go to Step 14.

NO Repair or replace it. Harness Connector Inspection.
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. Harness Connector Inspection.
Then go to Step 14.

STEP 8. Measure the sensor offset voltage at ECM [M/T] or PCM [A/T]
connector B-21 by using power plant ECU check harness special tool MB991923.









(1)Disconnect all ECM [M/T] connectors or PCM [A/T] connectors.
Connect the power plant ECU check harness special tool MB991923 between the separated connectors.
(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 [M/T] or PCM [A/T] for damage.





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 [M/T] or PCM [A/T] connector B-21 (terminal No. 105) because of open circuit or harness damage. Then go to Step 14.

NO Repair or replace it. Harness Connector Inspection.
Then go to Step 14.

STEP 10. Check harness connector B-21 at ECM [M/T] or PCM [A/T] for damage.





Q. Is the harness connector in good condition?

YES Go to Step 11.

NO Repair or replace it. Harness Connector Inspection.
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 [M/T] or PCM [A/T] connector B-21 (terminal No. 105).









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 [M/T] or PCM [A/T] connector B-21 (terminal No. 96).









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.
13. Transaxle: 2nd speed

14. Drive with wide open throttle

15. Engine: 3,500 r/min or more
Standard value: 0.6 - 1.0 V

(6)NOTE:
If the temperature of sensing area does not reach the high temperature [of approximately 400°C (752°F) or more]
even through the heated 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 voltage between 0.6 and 1.0 volt?

YES Replace the ECM or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Immobilizer System.
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 22 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.