13A-DTC P0137: Heated Oxygen Sensor Circuit Low Voltage

DTC P0137: Heated Oxygen Sensor (rear) Circuit Low Voltage

CIRCUIT OPERATION

A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM terminal O2RL from the output terminal of the heated oxygen sensor (rear).
Terminal ORLE of the heated oxygen sensor (rear) is grounded with ECM terminal ORLE.
The ECM applies an offset voltage of 0.5 volt to ground terminal of the heated oxygen sensor (rear).

TECHNICAL DESCRIPTION

The output signal of the linear air-fuel ratio sensor is compensated by the output signal of the heated oxygen sensor (rear).
The ECM checks for the heated oxygen sensor (rear) output voltage.

DESCRIPTIONS OF MONITOR METHODS

Heated oxygen sensor (rear) output voltage is under the specified range.

MONITOR EXECUTION

Continuous

MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)

Other Monitor (There is no temporary DTC set in memory for the item monitored below)

Linear air-fuel ratio sensor monitor
Linear air-fuel ratio sensor heater monitor
Heated oxygen sensor (rear) heater monitor
Heated oxygen sensor offset voltage monitor

Sensor (The sensor below is determined to be normal)

Mass airflow sensor
Engine coolant temperature sensor
Intake air temperature sensor
Barometric pressure sensor
Fuel tank pressure sensor

DTC SET CONDITIONS

Logic Flow Chart

Check Conditions

Power supply mode of electric motor switch is ON (READY).
Heated oxygen sensor offset voltage is between 0.4 and 0.6 volt.
12V starter battery positive voltage is between 11 and 16.5 volts.
The engine is running.
More than 3 minutes have passed since the engine starting sequence was completed.

Power supply mode of electric motor switch is ON.
Heated oxygen sensor offset voltage is between 0.4 and 0.6 volt.
12V starter battery positive voltage is between 11 and 16.5 volts.
The engine is stopped.
While the heated oxygen sensor (rear) heater is on.

Judgment Criterion

Heated oxygen sensor (rear) output voltage is lower than 0.2 volt for 2 seconds.

FAIL-SAFE AND BACKUP FUNCTION

None.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 2 .

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)

Heated oxygen sensor (rear) failed.
Open or shorted heated oxygen sensor (rear) circuit, harness damage or connector damage.
ECM failed.

DIAGNOSIS

Required Special Tools:

MB991658: Test Harness
MB992110: Power Plant ECU Check Harness

STEP 1. Using scan tool (M.U.T.-IIISE), check data list item AD: Heated Oxygen Sensor (rear).

caution

To prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch before connecting or disconnecting scan tool (M.U.T.-IIISE).

(1) Connect scan tool (M.U.T.-IIISE). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-IIISE)

(2) Set the vehicle to the continuous idling mode.

(3) Set scan tool (M.U.T.-IIISE) to the data reading mode for item AD, Heated Oxygen Sensor (rear).

The output voltages should be between 0.6 and 1.0 volt.

(4) Turn off the power supply mode of the electric motor switch.

Is the sensor operating properly?

It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions

Go to Step 2.

STEP 2. Measure the sensor output voltage at heated oxygen sensor (rear) connector.

(1) Disconnect the heated oxygen sensor (rear) connector and connect the test harness special tool MB991658 between the separated connectors.

(2) Set the vehicle to the continuous idling mode.

(3) Measure the voltage between terminal O2RL and ground.

The output voltage should be between 0.6 and 1.5 volts.

(4) Turn off the power supply mode of the electric motor switch.

Is the measured voltage within the specified range?

Go to Step 3.

Go to Step 4.

STEP 3. Measure the sensor output voltage at ECM connector by using power plant ECU check harness special tool MB992110.

(1) Disconnect all ECM connectors. Connect the power plant ECU check harness special tool MB992110 between the separated connectors.

(2) Set the vehicle to the continuous idling mode.

(3) Measure the voltage between terminal O2RL and ground.

The output voltage should be between 0.6 and 1.5 volts.

(4) Turn off the power supply mode of the electric motor switch.

Is the measured voltage between 0.6 and 1.5 volts?

Go to Step 8.

Repair or replace the connector(s), or check and repair the harness of open circuit and harness damage in O2RL line between heated oxygen sensor (rear) connector and ECM connector. Then go to Step 9.

STEP 4. Measure the sensor offset voltage at ECM connector by using power plant ECU check harness special tool MB992110.

(1) Disconnect all ECM connectors. Connect the power plant ECU check harness special tool MB992110 between the separated connectors.

(2) Turn on the power supply mode of the electric motor switch.

(3) Measure the voltage between terminal ORLE and ground.

Voltage should be between 0.4 and 0.6 volt.

(4) Turn off the power supply mode of the electric motor switch.

Is the measured voltage between 0.4 and 0.6 volt?

Go to Step 5.

Repair or replace the connector(s), or check and repair the harness of short to ground in ORLE line between heated oxygen sensor (rear) connector and ECM connector. Then go to Step 9.

STEP 5. Check of open circuit and harness damage in ORLE line between heated oxygen sensor (rear) connector and ECM connector.

Is the harness wire in good condition?

Go to Step 6.

Repair the connector(s) or wiring harness. Then go to Step 9.

STEP 6. Check of short circuit to ground in O2RL line between heated oxygen sensor (rear) connector and ECM connector.

Is the harness wire in good condition?

Go to Step 7.

Repair the connector(s) or wiring harness. Then go to Step 9.

STEP 7. Check the heated oxygen sensor (rear).

(1) Disconnect the heated oxygen sensor (rear) connector and connect test harness special tool MB991658 to the connector on the heated oxygen sensor (rear) side.

(2) Set the vehicle to the continuous idling mode.

(3) Warm up the engine until engine coolant temperature reaches 80°C (176°F) or higher.

(4) Rev the engine for 5 minutes or more with the engine speed of 2,000 r/min.

(5) Connect a digital voltage meter between terminal O2RL and terminal ORLE.

(6) While repeatedly revving the engine, measure the heated oxygen sensor (rear) output voltage.

Standard value: 0.6 - 1.0 V

note	If the temperature of sensing area does not reach the high temperature [of approximately 400°C (752°F) or more] even though the heated oxygen sensor is normal, the output voltage would be possibly low in spite of the rich air/fuel ratio.

note	When the vehicle is driven with high loads, the temperature of the sensing area of the heated oxygen sensor is sufficiently high. Thus, it is not necessary to apply the voltage to the heater.

Is the measured voltage between 0.6 and 1.0 volt?

Go to Step 8.

Replace the heated oxygen sensor (rear). Then go to Step 9.

STEP 8. Using scan tool (M.U.T.-IIISE), check data list item AD: Heated Oxygen Sensor (rear).

(1) Set the vehicle to the continuous idling mode.

(2) Set scan tool (M.U.T.-IIISE) to the data reading mode for item AD, Heated Oxygen Sensor (rear).

The output voltage should be between 0.6 and 1.0 volt.

(3) Turn off the power supply mode of the electric motor switch.

Is the sensor operating properly?

It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions

Replace the ECM (Refer to Removal and Installation

). Then go to Step 9.

STEP 9. 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 2

(2) Check the diagnostic trouble code (DTC).

Is DTC P0137 set?

Retry the troubleshooting.

The inspection is complete.