P0157
Left Bank Heated Oxygen Sensor (rear) Circuit:
Connectors:
CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal No.73)
- Terminal No.2 of the left bank heated oxygen sensor (rear) is grounded with ECM (terminal No. 49)
TECHNICAL DESCRIPTION
- The output signal of the heated oxygen sensor (front) is compensated by the output signal of the left bank heated oxygen sensor (rear).
- The ECM
DTC SET CONDITIONS
Check Conditions
- 3 minutes or more have passed since the starting sequence was completed.
- Left bank heated oxygen sensor (rear) signal voltage has continued to be 0.15 volt or lower.
- Engine coolant temperature is higher than 76 °C (169 °F).
- Engine speed is higher than 1,200 rpm.
- Volumetric efficiency is higher than 25 percent.
- Volume air flow sensor output frequency is 75 Hz or more.
- At least 20 seconds have passed since fuel shut off control was canceled.
- The left bank heated oxygen sensor (front) outputs 0.5 volt or more.
- After the ignition switch is turned ON, the changes in the output voltage of the left bank heated oxygen sensor (rear) is lower than 0.078 volt.
- Monitoring time: 10 seconds.
Judgement Criteria
- Making the air/fuel ratio 15 percent for 10 seconds richer does not result in raising the heated oxygen sensor (rear) output voltage beyond 0.15 volt.
- The ECM
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Left bank heated oxygen sensor (rear) failed.
- Short circuit in left bank heated oxygen sensor (rear) output line.
- ECM failed.
- PCM failed.
DIAGNOSIS
Required Special Tools:
- MB991502: Scan Tool (MUT-II)
- MB991316: Test Harness Set
STEP 1. Using scan tool MB991502, check data list item 59: Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).
CAUTION
To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 59, Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).
- Warming up the engine. When the engine is revved, the output voltage should repeat 0 volt 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. Refer to INTRODUCTION, How to Use Troubleshooting/Inspection Service Points.
NO: Go to Step 2.
STEP 2. 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 (front) side.
2. Warm up the engine until engine coolant 80 °C (176 °F) or higher.
CAUTION
Be very careful when connecting the jumper wires; incorrect connection can damage the right bank heated oxygen sensor (rear).
3. Use the jumper wires to connect terminal No.1 (red clip) to the positive battery terminal and terminal No.3 (blue clip) to the negative battery terminal.
4. Connect a digital volt meter between terminal No.2 (black clip) and terminal No.4 (white clip).
5. While repeatedly revving the engine, measure the left bank heated oxygen sensor (rear) output voltage.
Standard value: 0.6 - 1.0 volt
Q: Is the voltage between 0.6 and 1.0 volt?
YES: Go to Step 3.
NO: Replace the left bank heated oxygen sensor (rear). Then go to Step 5.
Connectors:
STEP 3. Check connector B-23 at left bank heated oxygen sensor (rear) and connector C-122 at ECM
Q: Is the connector in good condition?
YES: Go to Step 4
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 5.
Connectors:
STEP 4. Check for short circuit to ground between left bank heated oxygen sensor (rear) connector B-23 (terminal No.4) and ECM connector C-122 (terminal No.73)
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 5.
NO: Repair it. 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 Trouble Code Diagnosis - OBD-II Drive Cycle - Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0157 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.