P0136

DTC P0136: Heated Oxygen Sensor Circuit

Heated Oxygen Sensor (Rear) Circuit:

CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal No.73) from the output terminal (terminal No.4) of the heated oxygen sensor (rear).
- Terminal No.2 of the heated oxygen sensor (rear) is grounded with ECM (terminal No.49).

TECHNICAL DESCRIPTION
- The output signal of the heated oxygen sensor (front) is compensated by the output signal of the heated oxygen sensor (rear).
- The ECM checks for an open circuit in the heated oxygen sensor (rear) output line.

DESCRIPTIONS OF MONITOR METHODS
- Heated oxygen sensor (rear) circuit is switched to 5 volts intentionally when oxygen sensor output is low, and detects the malfunction if the output voltage changes to equal or greater than 4.5 volts. The above procedure is repeated when oxygen sensor is inactive.

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 heater (front) monitor
- Heated oxygen sensor heater (rear) monitor
- Air/fuel ratio feedback monitor

Sensor (The sensor below is determined to be normal)
- Volume airflow sensor
- Engine coolant temperature sensor
- Intake air temperature sensor
- Barometric pressure sensor

DTC SET CONDITIONS

Logic Flow Chart:

Logic Flow Chart

Check Conditions
- 3 minutes or more have passed since the engine starting sequence was completed.
- Heated oxygen sensor (rear) signal voltage has continued to be 0.15 volt or lower.
- Engine coolant temperature is higher than 76 degrees C (169 degrees F).
- Engine speed is higher than 1,200 r/min.
- Volumetric efficiency is higher than 25 percent.
- Monitoring time: 7 seconds.

Judgment Criterion
- Input voltage supplied to the ECM interface circuit is higher than 4.5 volts when 5 volts is applied to the heated oxygen sensor (rear) output line via a resistor.

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 11. OBD-II Drive Cycle Pattern Lists

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Heated oxygen sensor (rear) failed.
- Open or short circuit in heated oxygen sensor (rear) output line, or harness damage.
- Open circuit in heated oxygen sensor (rear) ground line, or harness damage.
- Connector damage.
- ECM failed.

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B
- MB991658: Test Harness Set

STEP 1. Using scan tool MB991958, check data list item 59: Heated Oxygen Sensor (rear).

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 59, Heated Oxygen Sensor (rear).
a. Transaxle: 2nd speed
b. Drive with wide open throttle
c. Engine: 3,500 r/min or more
- The output voltage 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.

NO: Go to Step 2.

STEP 2. Measure the sensor output voltage at heated oxygen sensor (rear) connector D-40 by backprobing.

1. Do not disconnect connector D-40.
2. Start the engine and run at idle.

3. Measure the voltage between terminal No.4 and ground by backprobing.
a. Transaxle: 2nd speed
b. Drive with wide open throttle
c. Engine: 3,500 r/min or more
- The output voltage should be between 0.6 and 1.0 volt.

4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the measured voltage within the specified range?

YES: Go to Step 3.

NO: Go to Step 7.

STEP 3. Measure the sensor output voltage at ECM connector C-117 by backprobing.

1. Do not disconnect connector C-117.
2. Start the engine and run at idle.

3. Measure the voltage between terminal No.73 and ground by backprobing.
a. Transaxle: 2nd speed
b. Drive with wide open throttle
c. Engine: 3,500 r/min or more
- The output voltage should be between 0.6 and 1.0 volt.

4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the measured voltage within the specified range?

YES: Go to Step 4.

NO: Go to Step 6.

STEP 4. Check harness connector D-40 at heated oxygen sensor (rear) and harness connector C-117 at ECM for damage.

Q: Is the harness connector in good condition?

YES: Go to Step 5.

NO: Repair or replace it. Then go to Step 14.

STEP 5. Using scan tool MB991958, check data list item 59: Heated Oxygen Sensor (rear).

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.

STEP 6. Check harness connector D-40 at heated oxygen sensor (rear) and harness connector C-117 at ECM for damage.

Q: Is the harness connector in good condition?

YES: Repair harness wire between heated oxygen sensor (rear) connector D-40 (terminal No.4) and ECM connector C-117 (terminal No.73) because of open circuit or harness damage. Then go to Step 14.

NO: Repair or replace it. Then go to Step 14.

STEP 7. Check harness connector D-40 at heated oxygen sensor (rear) for damage.

Q: Is the harness connector in good condition?

YES: Go to Step 8.

NO: Repair or replace it. Then go to Step 14.

STEP 8. Check for continuity at heated oxygen sensor (rear) harness side connector D-40.

1. Disconnect connector D-40 and measure at the harness side.

2. Check for the continuity between terminal No.2 and ground.
- Should be less than 2 Ohms.

Q: Does continuity exist?

YES: Go to Step 11.

NO: Go to Step 9.

STEP 9. Check harness connector C-119 at ECM for damage.

Q: Is the harness connector in good condition?

YES: Go to Step 10.

NO: Repair or replace it. Then go to Step 14.

STEP 10. Check for open circuit and harness damage between heated oxygen sensor (rear) connector D-40 (terminal No.2) and ECM connector C-119 (terminal No. 49).

Q: Is the harness wire in good condition?

YES: Replace the ECM. Then go to Step 14.

NO: Repair it. Then go to Step 14.

STEP 11. Check harness connector C-119 at ECM for damage.

Q: Is the harness connector in good condition?

YES: Go to Step 12.

NO: Repair or replace it. Then go to Step 14.

STEP 12. Check for harness damage between heated oxygen sensor (rear) connector D-40 (terminal No.2) and ECM connector C-119 (terminal No.49).

Q: Is the harness wire in good condition?

YES: Go to Step 13.

NO: Repair it. Then go to Step 14.

STEP 13. Check the heated oxygen sensor (rear).

1. Disconnect the heated oxygen sensor (rear) connector D-40 and connect test harness special tool, MB991658, to the connector on the heated oxygen sensor (rear) side.
2. Warm up the engine until engine coolant temperature reaches 80 degrees C (176 degrees 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.2 and terminal No.4.
5. Measure the output voltage of the heated oxygen sensor under the following driving.
- Transaxle: 2nd speed
- Drive with wide open throttle
- Engine: 3,500 r/min or more

Standard value: 0.6 - 1.0 volt

NOTE: If the sufficiently high temperature [of approximate 400 degrees C (752 degrees F) or more] is not reached although the heated oxygen sensor is normal, the output voltage would be possibly low although the rich air/fuel ratio.

Q: Is the voltage between 0.6 and 1.0 volt?

YES: Replace the ECM. Then go to Step 14.

NO: Replace the heated oxygen sensor (rear). Then go to Step 14.

STEP 14. 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 11. OBD-II Drive Cycle Pattern Lists
2. Check the diagnostic trouble code (DTC).

Q: Is DTC P0136 set?

YES: Retry the troubleshooting.

NO: The inspection is complete.