Technical Description of OBD-II Trouble Code
02 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
What is the meaning of this code?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The Powertrain control module (PCM) provides a .45 volt reference voltage to the Oxygen sensor. Once the O2 sensor reaches its operating temperature, it generates a voltage that varies based on the oxygen content in the exhaust. A lean exhaust produces a low voltage (less than .45V), while a rich exhaust produces a high voltage (greater than .45V).
O2 sensors labeled as “sensor 2” on a specific bank are used to monitor emissions. The Three-Way Catalyst (TWC) system, also known as the catalytic converter, is responsible for controlling tailpipe emissions. The PCM uses the signal received from Oxygen sensor 2 (indicated as #2, located aft of the catalytic converter) to assess the efficiency of the TWC. Normally, this sensor switches between high and low voltage at a slower rate compared to the front sensor, which is considered normal. However, if the signal from the rear (#2) O2 sensor indicates that the voltage has remained between .425V and .474V, the PCM determines that the sensor is inactive, and this code is triggered.
Potential Symptoms
Your check engine light (CEL) or malfunction indicator lamp (MIL) will illuminate. Apart from the MIL, you are unlikely to experience any noticeable drivability issues. This is because the rear or post-catalytic converter Oxygen sensor does not affect fuel delivery (except for Chryslers). Its role is solely to monitor the efficiency of the catalytic converter. Therefore, you will probably not notice any engine trouble.
Causes
The causes for a P0140 code are relatively limited. They may include:
Possible Solutions
This is a fairly specific problem and should not be too difficult to diagnose.
First, start the engine and let it warm up. Use a scan tool to monitor the voltage of Bank 1, sensor 2, O2 sensor. Normally, the voltage should switch slowly above and below .45 volts. If it does, the problem is likely intermittent, and you will have to wait for it to occur again before accurately diagnosing it.
However, if the voltage does not switch or remains stuck, follow these steps: 2. Turn off the vehicle. Inspect the Bank 1, sensor 2 harness connector visually for any signs of melting or chafing in the harness or connector. Repair or replace as necessary. 3. Turn the ignition on, but keep the engine off. Disconnect the O2 sensor connector and check for 12 volts on the Heater Circuit supply and for proper ground on the heater circuit ground circuit. a. If the 12V heater supply is missing, check the appropriate fuses for an open circuit. If the heater circuit fuse is blown, suspect a faulty heater in the O2 sensor, which caused the fuse to blow. Replace the sensor and fuse, and recheck. b. If the ground is missing, trace the circuit and clean or repair the ground circuit. 4. Next, with the connector still unplugged, check for 5 volts on the reference circuit. If it is missing, check for 5 volts at the PCM connector. If 5 volts is present at the PCM connector but not at the O2 sensor harness connector, there is likely an open or short in the reference wire supply between the PCM and the O2 sensor connector. However, if there is no 5 volts present at the PCM connector, the PCM is likely at fault due to an internal short. Replace the PCM. ** (NOTE: On Chrysler models, a common problem is that any sensor on the car using a 5 Volt reference can short out the 5 Volt reference circuit. Simply unplug each sensor one at a time until the 5 volts reappears. The last sensor you unplugged is the shorted sensor. Replacing it should resolve the 5 Volt reference short.) 5. If all the voltages and grounds are present, replace the Bank 1, sensor 2 O2 sensor and retest.
