P0161
Left Bank Heated Oxygen Sensor (Rear) Heater Circuit:
Connectors:
CIRCUIT OPERATION
- Power is supplied from the MFI relay (terminal 1) to the left bank heated oxygen sensor (rear) heater.
- The PCM (terminal 26) controls continuity to the left bank heated oxygen sensor (rear) heater by turning the power transistor in the PCM "ON" and "OFF".
BACKGROUND
- The PCM checks whether the heater current is within a specified range when the heater is energized.
DTC SET CONDITIONS
Check Conditions
- 60 seconds have elapsed from the start of the previous monitoring.
- Engine coolant temperature is higher than 20°C (68°F).
- While the left bank heated oxygen sensor (rear) heater is on.
- Battery positive voltage is between 11 and 16 volts.
Judgment Criteria
- Heater current of the left bank heated oxygen sensor (rear) heater has continued to be lower than 0.16 ampere or higher than 5.0 ampere for 4 seconds.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Open or shorted left bank heated oxygen sensor (rear) heater circuit.
- Open circuit in left bank heated oxygen sensor (rear) heater.
- PCM failed.
DIAGNOSIS
Required Special Tools
- MB991316: Test Harness Set
STEP 1. Check connector B-29 at the left bank heated oxygen sensor (rear) for damage.
Q: Is the connector in good condition?
YES: Go to Step 2.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 12.
STEP 2. Check the left bank heated oxygen sensor (rear).
1. Disconnect left bank heated oxygen sensor (rear) connector B-29 and connect test harness special tool, MB991316, to the connector on the left bank heated oxygen (rear) sensor side.
2. Measure the resistance between heated oxygen sensor connector terminal 1 (red clip) and terminal 3 (blue clip).
Standard value: 11 - 18 ohm [at 20°C (68°F)]
Q: Is the resistance normal?
YES: Go to Step 3.
NO: Replace the left bank heated oxygen sensor (rear). Then go to Step 12.
STEP 3. Check the power supply voltage at left bank heated oxygen sensor (rear) harness side connector B-29.
1. Disconnect the connector B-29 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 1 and ground.
- Voltage should be battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the voltage normal?
YES: Go to Step 5.
NO: Go to Step 4.
STEP 4. Check connector A-18X at the MFI relay for damage.
Q: Is the connector in good condition?
YES: Repair harness wire between MFI relay connector A-18X terminal 4 and left bank heated oxygen sensor (rear) connector B-29 terminal 1 because of open circuit or short circuit to ground. Then go to Step 12.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 12.
STEP 5. Check the power supply voltage at PCM connector C-39 by backprobing.
1. Do not disconnect the connector C-39.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 26 and ground by backprobing.
- Voltage should be battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the voltage normal?
YES: Go to Step 8.
NO: Go to Step 6.
STEP 6. Check connector C-39 at PCM for damage.
Q: Is the connector in good condition?
YES: Go to Step 7.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 12.
STEP 7. Check for open circuit or short circuit to ground between left bank heated oxygen sensor (rear) connector B-29 terminal 3 and PCM connector C-39 terminal 26.
Q: Is the harness wire in good condition?
YES: Replace the PCM. Then go to Step 12.
NO: Repair it. Then go to Step 12.
STEP 8. Check connector C-39 at PCM for damage.
Q: Is the connector in good condition?
YES: Go to Step 9.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 12.
STEP 9. Check for harness damage between MFI relay connector A-18X terminal 4 and left bank heated oxygen sensor (rear) connector B-29 terminal 1.
Q: Is the harness wire in good condition?
YES: Go to Step 10.
NO: Repair it. Then go to Step 12.
STEP 10. Check for harness damage between left bank heated oxygen sensor (rear) connector B-29 terminal 3 and PCM connector C-39 terminal 26.
Q: Is the harness wire in good condition?
YES: Go to Step 11.
NO: Repair it. Then go to Step 12.
STEP 11. Check the trouble symptoms.
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is the DTC P0161 is output?
YES: Replace the PCM. Then go to Step 12.
NO: It can be assumed that this malfunction is intermittent.
Refer to How to Use Troubleshooting/Inspection Service Points.
STEP 12. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is the DTC P0161 is output?
YES: Retry the troubleshooting.
NO: The inspection is complete.