P0144

DTC P0144: Heated Oxygen Sensor (3rd) Circuit High Voltage [Vehicles for California]










CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal No. 54) from the output terminal (terminal No. 3) of the heated oxygen sensor (3rd).
- Terminal No. 4 of the heated oxygen sensor (3rd) is grounded with ECM (terminal No. 55).
- The ECM applies an offset voltage of 0.5 volt to terminal No. 4 of the heated oxygen sensor (3rd).

TECHNICAL DESCRIPTION
- The ECM checks for the heated oxygen sensor (3rd) output voltage.

DESCRIPTIONS OF MONITOR METHODS
Heated oxygen sensor (3rd) output voltage is over 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)
- Linear air-fuel ratio sensor monitor
- Linear air-fuel ratio sensor heater monitor
- Heated oxygen sensor offset voltage monitor
- Heated oxygen sensor heater (3rd) 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







Check Conditions
- More than 2 seconds have passed since the engine starting sequence was completed.
- Heated oxygen sensor offset voltage is between 0.4 and 0.6 volt.

Judgement Criterion
- Heated oxygen sensor (3rd) output voltage is more than 1.8 volts for 2 seconds.

FAIL-SAFE AND BACKUP FUNCTION
- None

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 23. OBD- II Drive Cycle

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Short circuit in heated oxygen sensor (3rd) output line.
- Connector damage.
- ECM failed.

DIAGNOSIS

Required Special Tool:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A

STEP 1. Using scan tool MB991958, check data list item B1: Heated Oxygen Sensor (3rd).







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 B1, Heated Oxygen Sensor (3rd).
a. Transaxle: 2nd speed
b. Drive with wide open throttle
c. Engine: 3,500 r/min or more
- 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. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction Troubleshooting Contents

NO : Go to Step 2.

STEP 2. Check harness connector D-31 at heated oxygen sensor (3rd) and harness connector B-108 at ECM for damage.

Q: Are the harness connectors in good condition?

YES : Go to Step 3.

NO : Repair or replace them. Then go to Step 5.

STEP 3. Check for short circuit to power supply between heated oxygen sensor (3rd) connector D-31 (terminal No. 3) and ECM connector B-108 (terminal No. 54).

NOTE: Check harness after checking intermediate connectors A-10 and C-37. If intermediate connectors are damaged, repair or replace them. Then go to Step 5.

Q: Is the harness wire in good condition?

YES : Go to Step 4.

NO : Repair it. Then go to Step 5.

STEP 4. Using scan tool MB991958, check data list item B1: Heated Oxygen Sensor (3rd).

1. Start the engine and run at idle.
2. Set scan tool MB991958 to the data reading mode for item B1, Heated Oxygen Sensor (3rd).
a. Transaxle: 2nd speed
b. Drive with wide open throttle
c. Engine: 3,500 r/min or more
- The output voltages should be between 0.6 and 1.0 volt.

3. 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 - How to Cope with Intermittent Malfunction Troubleshooting Contents

NO : Replace the ECM. 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 Diagnostic Function - OBD-II Drive Cycle - Pattern 23. OBD- II Drive Cycle
2. Check the diagnostic trouble code (DTC).

Q: Is DTC P0144 set?

YES : Retry the troubleshooting.

NO : The inspection is complete.