P0051
DTC P0051: Heated Oxygen Sensor Heater Control Circuit Low (bank 2, sensor 1)Left Bank Heated Oxygen Sensor (front) Heater Circuit Part 1:
Left Bank Heated Oxygen Sensor (front) Heater Circuit Part 2:
CIRCUIT OPERATION
- Power is supplied from the MFI relay (terminal No. 4) to the left bank heated oxygen sensor (front) heater.
- The PCM (terminal No. 125) controls continuity to the left bank heated oxygen sensor (front) heater by turning the power transistor in the PCM "ON" and "OFF".
TECHNICAL DESCRIPTION
- The PCM checks whether the heater current is within a specified range when the heater is energized.
- The PCM checks whether the heater voltage is within a specified range when the heater is not energized.
DESCRIPTIONS OF MONITOR METHODS
Left bank heated oxygen sensor heater (front) current or voltage is out of 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)
- Not applicable
Sensor (The sensor below is determined to be normal)
- Engine coolant temperature sensor
DTC SET CONDITIONS
Logic Flow Chart:
Logic Flow Chart
Check Conditions
- More than 2 seconds have passed since the engine starting sequence was completed.
- While the left bank heated oxygen sensor (front) heater is on.
- Battery positive voltage is at between 11 and 16.5 volts.
Judgement Criterion
- The left bank heated oxygen sensor (front) heater current has continued to be lower than 0.17 ampere for 2 seconds.
Check Conditions
- More than 2 seconds have passed since the engine starting sequence was completed.
- While the right bank heated oxygen sensor (front) heater is off.
- Battery positive voltage is at between 11 and 16.5 volts.
Judgement Criterion
- The right bank heated oxygen sensor (front) heater voltage has continued to be lower than 2.0 voltage for 2 seconds.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 2. OBD-II Drive Cycle
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Open or shorted left bank heated oxygen sensor (front) heater circuit, or harness damage.
- Left bank heated oxygen sensor (front) heater.
- Connector damage.
- PCM failed.
DIAGNOSIS
Required Special Tools:
- MD998464: Test Harness
- MB991923: Check Harness
STEP 1. Check harness connector B-25 at the left bank heated oxygen sensor (front) for damage.
Q: Is the harness connector in good condition?
YES: Go to Step 2.
NO: Repair or replace it. Then go to Step 12.
STEP 2. Check the left bank heated oxygen sensor (front).
1. Disconnect left bank heated oxygen sensor (front) connector B-25 and connect test harness special tool, MD998464, to the connector on the left bank heated oxygen (front) sensor side.
2. Measure the resistance between heated oxygen sensor connector terminal No. 1 (red clip) and terminal No. 3 (blue clip).
Standard value: 4.5 - 8.0 Ohms [at 20 °C (68 °F)]
Q: Is the measured resistance between 4.5 and 8.0 Ohms [at 20 °C (68 °F)]?
YES: Go to Step 3.
NO: Replace the left bank heated oxygen sensor (front). Then go to Step 12.
STEP 3. Measure the power supply voltage at left bank heated oxygen sensor (front) harness side connector B-25.
1. Disconnect the connector B-25 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 1 and ground.
- Voltage should be battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts) present?
YES: Go to Step 5.
NO: Go to Step 4.
STEP 4. Check harness connector B-15X at the MFI relay for damage.
Q: Is the harness connector in good condition?
YES: Repair harness wire between MFI relay connector B-15X (terminal No. 4) and left bank heated oxygen sensor (front) connector B-25 (terminal No. 1) because of open circuit or short circuit to ground. Then go to Step 12.
NO: Repair or replace it. Then go to Step 12.
STEP 5. Measure the power supply voltage at PCM connector B-22 by using power plant ECU check harness special tool MB991923.
1. Disconnect all PCM 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. 125 and ground.
- Voltage should be battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts) present?
YES: Go to Step 8.
NO: Go to Step 6.
STEP 6. Check harness connector B-22 at PCM for damage.
Q: Is the harness connector in good condition?
YES: Go to Step 7.
NO: Repair or replace it. Then go to Step 12.
STEP 7. Check for open circuit or short circuit to ground between left bank heated oxygen sensor (front) connector B-25 (terminal No. 3) and PCM connector B-22 (terminal No. 125).
Q: Is the harness wire in good condition?
YES: Replace the PCM. When the PCM is replaced, register the encrypted code. Refer to Encrypted Code Registration Criteria Table. Then go to Step 12.
NO: Repair it. Then go to Step 12.
STEP 8. Check harness connector B-22 at PCM for damage.
Q: Is the harness connector in good condition?
YES: Go to Step 9.
NO: Repair or replace it. Then go to Step 12.
STEP 9. Check for harness damage between MFI relay connector B-15X (terminal No. 4) and left bank heated oxygen sensor (front) connector B-25 (terminal No. 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 (front) connector B-25 (terminal No. 3) and PCM connector B-22 (terminal No. 125).
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 Diagnostic Function - OBD-II Drive Cycle - Pattern 2. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0051 set?
YES: Replace the PCM. When the PCM is replaced, register the encrypted code. Refer to Encrypted Code Registration Criteria Table. Then go to Step 12.
NO: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.
STEP 12. 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 2. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0051 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.