P0156
Connectors:
CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal 73)
- Terminal 2 of the left bank heated oxygen sensor (rear) is grounded with ECM (terminal 49)
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
DTC SET CONDITIONS
Check Conditions
- Left bank heated oxygen sensor (rear) signal voltage has continued to be 0.15 volt or lower for three minutes or more after the starting sequence was completed.
- Engine coolant temperature is higher than 82 °C (180 °F).
- Engine speed is higher than 1,200 r/min.
- Volumetric efficiency is higher than 25 percent.
- Monitoring time: 7 seconds.
Judgment Criteria
- Input voltage supplied to the ECM
- Only one monitor during one drive cycle
Check Conditions
- Left bank heated oxygen sensor (rear) signal voltage has continued to be 0.15 volt or lower for three minutes or more after the starting sequence was completed.
- Engine coolant temperature is higher than 82 °C (180 °F).
- Engine speed is higher than 1,200 r/min.
- Volumetric efficiency is higher than 25 percent.
- Volume air flow sensor output frequency is 75 Hz or more.
- At least twenty seconds have passed since fuel shut off control was canceled.
- The left bank heated oxygen sensor (front) outputs 0.5 volts or more.
- Monitoring time: 10 seconds
Judgement Criteria
- Making the air/fuel ratio 15 percent for 10 seconds richer does not result in raising the left bank heated oxygen sensor (rear) output voltage beyond 0.15 volt.
- Only one monitor during one drive cycle
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Left bank heated oxygen sensor (rear) failed.
- Open circuit in left bank heated oxygen sensor (rear) output line.
- Open circuit in left bank heated oxygen sensor (rear) ground line.
- ECM failed.
- PCM failed.
DIAGNOSIS
Required Special Tools
MB991502: Scan Tool(MUT-II)
MB991316: Test Harness
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 (let 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 How to Use Troubleshooting/Inspection Service Points.
NO: Go to Step 2.
STEP 2. Check 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 4 and ground by backprobing.
- 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 voltage normal?
YES: Go to Step 3.
NO: Go to Step 7.
STEP 3. Check the sensor output voltage at ECM connector C-122
1. Do not disconnect the connector C-122
2. Stan the engine and run at idle.
3. Measure the voltage between terminal 73 and ground by backprobing.
- Warming up the engine. When the engine is 2,500 r/min, 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 voltage normal?
YES: Go to Step 4.
NO: Go to Step 6.
STEP 4. 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 5.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 15.
STEP 5. 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 repeal 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: 11 can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points.
NO: Replace the ECM or PCM. Then go to Step 15.
STEP 6. 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: Repair harness wire between left bank heated oxygen sensor (rear) connector B-23 terminal 4 and ECM connector C-122 terminal 73
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 15.
STEP 7. Check connector B-23 at left bank heated oxygen sensor (rear) for damage.
Q: Is the connector in good condition?
YES: Go to Step 8.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 15.
STEP 8. Check the continuity at left bank heated oxygen sensor (rear) harness side connector B-23.
1. Disconnect the connector B-23 and measure at the harness side.
2. Check for the continuity between terminal 2 and ground. Should be less than 2 Ohms.
Q: Is the continuity normal?
YES: Go to Step 11.
NO: Go to Step 9.
STEP 9. Check connector C-118 at ECM
Q: Is the connector in good condition?
YES: Go to Step 10.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 15.
STEP 10. Check for open circuit and harness damage between left bank heated oxygen sensor (rear) connector B-23 terminal 2 and ECM connector C-118 terminal 49
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 15.
NO: Repair it. Then go to Step 15.
STEP 11. Check connector C-122 at ECM
Q: Is the connector in good condition?
YES: Go to Step 12.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 15.
STEP 12. Check for harness damage between left bank heated oxygen sensor (rear) connector B-23 terminal 2 and ECM connector C-118 terminal 49
Q: Is the harness wire in good condition?
YES: Go to Step 13.
NO: Repair it. Then go to Step 15.
STEP 13. Check for short circuit to ground and harness damage between left bank heated oxygen sensor (rear) connector B-23 terminal 4 and ECM connector C-122 terminal 73
Q: Is the harness wire in good condition?
YES: Go to Step 14.
NO: Repair it. Then go to Step 15.
STEP 14. 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 left bank heated oxygen sensor (rear).
3. Use the jumper wires to connect terminal 1 (red clip) to the positive battery terminal and terminal 3 (blue clip) to the negative battery terminal.
4. Connect a digital volt meter between terminal 2 (black clip) and terminal 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 V
Q: Is the voltage at the standard value?
YES: Replace the ECM or PCM. Then go to Step 15.
NO: Replace the left bank heated oxygen sensor (rear).
Then go to Step 15.
STEP 15. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 4 - Heated oxygen Sensor Monitor and Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code(DTC).
Q: Is the DTC P0156 is output?
YES: Retry the troubleshooting.
NO: The inspection is complete.