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)
- 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
DESCRIPTIONS OF MONITOR METHODS
- The output of the heated oxygen sensor (rear) is monitored when the air-fuel mixture is forcefully made richer, and if the sensor output remains low and unchanged, a malfunction is determined to have occurred.
MONITOR EXECUTION
- Once per driving cycle
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC stored in memory for the item monitored)
- Not applicable
Sensor (The sensor is determined to be normal)
- Not applicable
DTC SET CONDITIONS
Logic Flow Chart:
Logic Flowchart
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 81 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 for 10 seconds richer does not result in raising the heated oxygen sensor (rear) output voltage beyond 0.15 volt.
- The ECM
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 6 - Other Monitor. OBD-II Drive Cycle Pattern Lists
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.
- ECM failed.
- PCM failed.
DIAGNOSIS
Required Special Tools:
- 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 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).
- 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 C-11 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.
3. Perform a racing for 5 minutes or more with the engine speed of 4,500 r/min.
4. Connect a digital voltage meter between terminal No. 1 and terminal No. 2.
5. While repeatedly revving the engine, measure the heated oxygen sensor (front) output voltage.
Standard value: 0.6 - 1.0 volt
CAUTION:
- Be very careful when connecting the jumper wire; incorrect connection can damage the heated oxygen sensor (rear).
- Be careful the heater is broken when voltage of beyond 12 volts is applied to the heated oxygen sensor (rear) heater.
NOTE: If the sufficiently high temperature [of approximate 400 °C (752 °F) or more] is not reached although the heated oxygen sensor (rear) is normal, the output voltage would be possibly low although the rich air/fuel ratio. Therefore, if the output voltage is low, use a jumper wire to connect the terminal No. 3 and the terminal No.4 of the heated oxygen sensor (rear) with the positive terminal and the negative terminal of 12 volts power supply respectively, then check again.
Q: Is the measured 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 C-11 at heated oxygen sensor (rear) and harness connector C-115 at ECM
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 C-11 (terminal No. 1) and ECM connector C-115 (terminal No. 75)
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 5.
NO: Repair it. 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 - Procedure 6 - Other Monitor. OBD-II Drive Cycle Pattern Lists
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0137 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.