P0143
DTC P0143: Heated Oxygen Sensor Circuit Low Voltage (bank 1, sensor 3) [California]Center Exhaust Pipe Heated Oxygen Sensor Circuit (Part 1):
Center Exhaust Pipe Heated Oxygen Sensor Circuit (Part 2):
CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal No. 101) from the output terminal (terminal No. 3) of the Center exhaust pipe heated oxygen sensor.
- Terminal No. 4 of the Center exhaust pipe heated oxygen sensor is grounded with ECM (terminal No. 116).
- The ECM applies an off set voltage of 0.5 volt to terminal No. 4 of the Center exhaust pipe heated oxygen sensor.
TECHNICAL DESCRIPTION
The ECM checks for the center exhaust pipe heated oxygen sensor output voltage.
DESCRIPTIONS OF MONITOR METHODS
Center exhaust pipe heated oxygen sensor output voltage is under the 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)
- Heated oxygen sensor (front) monitor
- Heated oxygen sensor (front) heater monitor
- Heated oxygen sensor (front) inactive monitor
- Heated oxygen sensor offset voltage monitor
- Air/fuel ratio feedback monitor
- Center exhaust pipe heated oxygen sensor heater 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
Logic Flow Chart:
Check Conditions
- Heated oxygen sensor offset voltage is between 0.4 and 0.6 volt.
- Battery positive voltage is between 11 and 16.5 volts.
- 3 minutes or more have passed since the engine starting sequence was completed.
Judgement Criterion
- Center exhaust pipe heated oxygen sensor output voltage is lower than 0.2 volt for 2 seconds.
OBD-II DRIVE CYCLE PATTERN
Refer to MFI 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:)
- Center exhaust pipe Heated oxygen sensor failed.
- Connector damage.
- Harness damage
- ECM failed.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
- MB991658: Test Harness
STEP 1. Check harness connector D-30 at the center exhaust pipe heated oxygen sensor and harness connector B-11 at the ECM for damage.
Q: Is the harness connector in good condition?
YES : Go to Step 2.
NO : Repair it. Refer to General (Electrical), Harness Connector Inspection. Then go to Step 4.
STEP 2. Check the center exhaust pipe heated oxygen sensor.
1. Disconnect the center exhaust pipe heated oxygen sensor connector D-30 and connect test harness special tool, MB991658, to the connector on the center exhaust pipe heated oxygen sensor side.
2. Warm up the engine until engine coolant temperature reaches 80 °C (176 °F) or higher.
3. Drive at 50 km/h (31 mph) or more for 10 minutes.
4. Connect a digital voltage meter between terminal No. 3 and terminal No. 4.
5. Measure the output voltage of heated oxygen sensor under the following driving.
a. Transaxle: 2nd speed
b. Drive with wide open throttle
c. Engine: 3,500 r/min or more
Standard value: 0.6 - 1.0 volts
NOTE: If the temperature of sensing area does not reach the high temperature [of approximately 400 °C (752 °F) or more] even though the oxygen sensor is normal, the output voltage would be possibly low in spite of the rich air-fuel ratio.
Q: Is the voltage between 0.6 and 1.0 volts?
YES : Go to Step 3.
NO : Replace the center exhaust pipe heated oxygen sensor. Then go to Step 4.
STEP 3. Check for harness between the center exhaust pipe heated oxygen sensor connector D-30 and the ECM connector B-11.
1. Disconnect the center exhaust pipe heated oxygen sensor connector D-30 and the ECM connector B-11.
2. Measure the resistance between the center exhaust pipe heated oxygen sensor connector D-30 and the ECM connector B-11.
a. Connector D-30 (terminal No. 4) and connector B-11 (terminal No. 116).
b. Connector D-30 (terminal No. 3) and connector B-11 (terminal No. 101).
- Should be less than 2 ohms.
3. Check for the continuity between the oxygen sensor connector D-30 and ground.
a. Connector D-30 (terminal No. 4) and ground
b. Connector D-30 (terminal No. 3) and ground
- Not continuity.
Q: Is the harness wire in good condition?
YES : Go to Step 4.
NO : Repair it. Refer to General (Electrical), Harness Connector Inspection. Then go to Step 4.
STEP 4. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to MFI Diagnostic Function-OBD-II Drive Cycle-Pattern 23. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0137 set?
YES : Replace the ECM. When the ECM is replaced,register the ID code. Refer to Diagnosis-ID Codes Registration Judgment Table [Vehicles with KOS] or Diagnosis-ID Codes Registration Judgment Table [Vehicles with WCM].
NO : It can be assumed that this malfunction is intermittent. Refer to General (Body and Chassis), How to Use Troubleshooting/Inspection Service Points How to Cope with Intermittent Malfunctions.