Vehicles For California

DTC P0140: Heated Oxygen Sensor (rear) Circuit No Activity Detected [Vehicles for California]


















CIRCUIT OPERATION

- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal No. 40) from the output terminal (terminal No. 3) of the heated oxygen sensor (rear).
- Terminal No. 4 of the heated oxygen sensor (rear) is grounded with ECM (terminal No. 41).
- The ECM applies an offset voltage of 0.5 volt to terminal No. 4 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 does not change during specified go/stop operations including fuel cut are repeated.

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)

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

DTC SET CONDITIONS

Logic Flow Chart






Check Conditions

- Engine coolant temperature is more than 76°C (169°F).
- The linear air-fuel ratio sensor is active.
- The cumulative mass airflow sensor output is more than 1,638 g.
- Repeat 1 time or more: drive*1, stop*2.
Drive*1:
- Engine speed is more than 1,500 r/min.
- Volumetric efficiency is more than 40 percent.
- Vehicle speed is more than 30 km/h (19 mph).
- A total of more than 60 seconds have passed with the above mentioned conditions, and more than 3 seconds have passed with the fuel shut off.
Stop*2:
- Vehicle speed is less than 1.5 km/h (1 mph).
Judgement Criterion

- Change in the output voltage of the heated oxygen sensor (rear) is less than 0.313 volt.
or

- The maximum output voltage of the heated oxygen sensor (rear) is less than 0.508 volt.

NOTE:
Monitoring stops after fuel has been shut off for more than 64 seconds.

FAIL-SAFE AND BACKUP FUNCTION

- None

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 13 Monitors, Trips, Drive Cycles and Readiness Codes .

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

- Heated oxygen sensor (rear) deteriorated.
- Connector damage.
- ECM failed.

DIAGNOSIS

Required Special Tool:

- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A

STEP 1. Using scan tool MB991958, check data list item AD: 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 AD, Heated Oxygen Sensor
(rear).
1. Transaxle: 2nd speed

2. Drive with wide open throttle

3. Engine: 3,500 r/min or more

- The output voltages 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. How to Cope With Intermittent Malfunctions.

NO Replace the heated oxygen sensor (rear). Then go to Step 2.

STEP 2. 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 13 Monitors, Trips, Drive Cycles and Readiness Codes.

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

Q. Is DTC P0140 set?

YES Refer to DTC P0137 - Heated Oxygen Sensor (rear) Circuit Low Voltage [Vehicles for California] Vehicles For California, DTC P0138 - Heated Oxygen Sensor
(rear) Circuit High Voltage [Vehicles for California] Vehicles For California.
NO The inspection is complete.