P0137

DTC P0137: HEATED OXYGEN SENSOR CIRCUIT LOW VOLTAGE (SENSOR 2)

Heated Oxygen Sensor (Rear) Circuit Part 1:

Heated Oxygen Sensor (Rear) Circuit Part 2:

CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal No. 75) from the output terminal (terminal No. 1) of the heated oxygen sensor (rear).
- Terminal No. 2 of the heated oxygen sensor (rear) is grounded with ECM (terminal No. 92).

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.

DTC SET CONDITIONS

Check Conditions
- 3 minutes or more have passed since the 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 °C (169 °F).
- Engine speed is higher than 1,200 r/min.
- Volumetric efficiency is higher than 25 percent.
- Volume airflow sensor output frequency is 56 Hz or more.
- At least 20 seconds have passed since fuel shut off control was canceled.
- The heated oxygen sensor (front) outputs 0.5 volt or more.
- After the ignition switch is turned ON, the changes in the output voltage of the heated oxygen sensor (rear) is lower than 0.078 volt.
- Monitoring time: 10 seconds.

Judgement Criteria
- Making the air/fuel ratio 15 percent richer for 10 seconds does not result in raising the heated oxygen sensor (rear) output voltage beyond 0.15 volt.
- The ECM monitors for this condition once during the drive cycle.

TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CODE TO BE SET ARE:)
- Heated oxygen sensor (rear) failed.
- Short circuit in heated oxygen sensor (rear) output line.
- Connector damage.
- ECM failed.

DIAGNOSIS

Required Special Tools:
- MB991502: Scan Tool (MUT-II)
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B
- MB991658: Test Harness Set

STEP 1. Using scan tool MB991502 or MB991958, check data list item 59: Heated Oxygen Sensor (rear).









CAUTION: To prevent damage to scan tool MB991502 or MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502 or MB991958.

1. Connect scan tool MB991502 or MB991958 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 or MB991958 to the data reading mode for item 59, Heated Oxygen Sensor (rear).
- Warm up the engine. When the engine is revved, the output voltage should repeat 0 volt and 0.6 to 1.0 volt alternately.

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.

NO: Go to Step 2.

STEP 2. 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 (front) side.
2. Warm up the engine until engine coolant 80 °C (176 °F) or higher.

CAUTION: Be very careful when connecting the jumper wires; incorrect connection can damage the right bank heated oxygen sensor (rear).




3. Use the jumper wires to connect terminal No. 3 to the positive battery terminal and terminal No. 4 to the negative battery terminal.
4. Connect a digital volt meter between terminal No 1 and terminal No. 2.
5. While repeatedly revving the engine, measure the heated oxygen sensor (rear) output voltage.

Standard value: 0.6 - 1.0 volt

Q: Is the voltage between 0.6 and 1.0 volt?

YES: Go to Step 3.

NO: Replace the heated oxygen sensor (rear). Then go to Step 5.







STEP 3. Check harness connector D-40 at heated oxygen sensor (rear) and connector C-115 at ECM for damage.

Q: Is the harness connector in good condition?

YES: Go to Step 4.

NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 5.







STEP 4. Check for short circuit to ground between heated oxygen sensor (rear) connector D-40 (terminal No. 1) and ECM connector C-115 (terminal No. 75).

Q: Is the harness wire in good condition?

YES: Replace the ECM. Then go to Step 5.

NO: Repair it. Then go to Step 5.

STEP 5. Perform the OBD-II drive cycle.

1. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code (DTC).

Q: Is DTC P0137 set?

YES: Repeat the troubleshooting.

NO: The procedure is complete.