13B-DTC P0157: Heated Oxygen Sensor Circuit Low Voltage

DTC P0157: Heated Oxygen Sensor Circuit Low Voltage (bank 2, sensor 2)

CIRCUIT OPERATION

A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM terminal O2RL from the output terminal (terminal No. 4) of the left bank heated oxygen sensor (rear).
Terminal No. 2 of the left bank 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 left bank heated oxygen sensor (rear).

TECHNICAL DESCRIPTION

The output signal of the left bank heated oxygen sensor (front) is compensated by the output signal of the left bank heated oxygen sensor (rear).
The ECM check for the left bank heated oxygen sensor (rear) output voltage.

DESCRIPTIONS OF MONITOR METHODS

Left bank heated oxygen sensor (rear) out put 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)

Left bank linear air-fuel ratio sensor monitor
Left bank heated oxygen sensor (rear) heater monitor
Left bank linear air-fuel ratio sensor heater monitor
Left bank linear air-fuel ratio sensor inactive monitor
Heated oxygen sensor offset voltage monitor
Air/fuel ratio feedback monitor

Sensor (The sensor below is determined to be normal)

Mass airflow sensor
Engine coolant temperature sensor
Intake air temperature sensor
Barometric pressure sensor
Throttle position 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.

Judgment Criterion

Left bank 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 21 .

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

Left bank heated oxygen sensor (rear) failed.
Connector damage.
Harness damage.
ECM failed.

DIAGNOSIS

Required Special Tools:

MB992744: Vehicle Communication Interface-Lite (V.C.I.-Lite)
MB992745: V.C.I.-Lite Main Harness A
MB992747: V.C.I.-Lite USB Cable Short
MB992748: V.C.I.-Lite USB Cable Long
MB991958: Scan Tool (M.U.T.-III Sub Assembly)

MB991824: Vehicles Communication Interface (V.C.I.)
MB991827: M.U.T.-III USB Cable
MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)

MB991316: Test Harness

STEP 1. Using scan tool (M.U.T.-III), check data list item AF: Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).

caution

To prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).

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

(2) Start the engine and run at idle.

(3) Set scan tool (M.U.T.-III) to the data reading mode for item AF, Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).

Transaxle: 2nd
Drive with wide open throttle
Engine: 3,500 r/min

The output voltages should be between 0.6 and 1.0 volt.

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

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 left bank heated oxygen sensor (rear) connector by backprobing

(1) Do not disconnect the left bank heated oxygen sensor (rear) connector.

(2) Start the engine and run at idle.

(3) Measure the voltage between terminal O2RL line and ground by backprobing under the following driving.

Transaxle: 2nd
Drive with wide open throttle
Engine: 3,500 r/min or more

The output voltage should be between 1.0 and 1.5 volts.

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

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) Start the engine and run at idle.

(3) Measure the voltage between terminal O2RL and ground by backprobing under the following driving.

Transaxle: 2nd
Drive with wide open throttle
Engine: 3,500 r/min or more

The output voltage should be between 1.0 and 1.5 volts.

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

Is the measured voltage between 1.0 and 1.5 volts?

Go to Step 4.

Repair or replace the connector(s), or check and repair the harness of open circuit and harness damage in O2RL line between left bank 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 the ignition switch to the "ON" position.

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

Voltage should be between 0.4 and 0.6 volt.

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

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 left bank 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 left bank 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 left bank 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 left bank heated oxygen sensor (rear).

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

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

(3) Drive at 50 km/h (31mph) or more for 10 minutes.

(4) Connect a digital voltage meter between terminal O2RL line and terminal O2LE line.

(5) Measure the output voltage of heated oxygen sensor under the following driving.

Transaxle: 2nd
Drive with wide open throttle
Engine: 3,500 r/min or more

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 left bank heated oxygen sensor (rear). Then go to Step 9.

STEP 8. Using scan tool (M.U.T.-III), check data list item AF: Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).

(1) Start the engine and run at idle.

(2) Set scan tool (M.U.T.-III) to the data reading mode for item AF, Heated Oxygen Sensor Bank 2, Sensor 2 (left rear).

Transaxle: 2nd
Drive with wide open throttle
Engine: 3,500 r/min or more

The output voltage should be between 0.6 and 1.0 volt.

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

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 21

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

Is DTC P0157 set?

Retry the troubleshooting.

The inspection is complete.