P0140 02 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
OBD-II Trouble Code Technical Description
02 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles. Although generic, the specific repair steps may vary depending on make/model.
The Powertrain control module (PCM) will provide a .45 volt reference voltage to the Oxygen sensor. When the O2 sensor reaches operating temperature, it will generate a voltage that will vary depending on the oxygen content of the exhaust. Lean exhaust generates a low voltage (less than .45V) and rich exhaust generates a high voltage (greater than .45V).
O2 sensors on a specific bank marked as "sensor 2" (as this one is) are used to monitor emissions. A Three-Way Catalyst (TWC) system (catalytic converter) is used to control tailpipe emissions. The PCM uses the signal received from Oxygen sensor 2 (#2 indicates aft of catalytic converter, #1 indicates pre-converter) to read efficiency of TWC. Normally this sensor will switch between high and low voltage at a noticeably slower rate than the front sensor. This is normal. If the signal received from rear (#2) O2 sensor indicates that the voltage has "stuck" between .425V to .474 V, the PCM determines this sensor is inactive and this code will set.
Potential Symptoms
Your check engine light(CEL), or malfuction indicator lamp (MIL) will be illuminated. There will not likely be any noticeable drivability problems other than the MIL. The reason is this: The rear or post catalytic converter Oxygen sensor does not affect fuel deliver(this is an exception on Chryslers). It only MONITORS the efficiency of the catalytic converter. For this reason, you will likely not notice any engine trouble.
Causes
The causes for a P0140 code are fairly few. They could be any of the following:
Possible Solutions
This is a fairly specific problem and shouldn’t be too difficult to diagnose.
First, start engine and warm up. Using a scan tool, watch the Bank 1, sensor 2, o2 sensor voltage. Normally the voltage should switch slowly above and below .45 volts. If it does, the problem is likely intermittent. You’ll have to wait for the problem to surface before you can accurately diagnose.
However, if it doesn’t switch, or is stuck then perform the following: 2. Shut off vehicle. Visually check the Bank1,2 harness connector for melting or chafing of the harness or the connector. Repair or replace as needed 3. Turn ignition on, but engine off. Disconnect the O2 sensor connector and check for 12Volts at the Heater Circuit supply and for proper ground on the heater circuit ground circuit. a. If 12V heater supply is missing, check the proper fuses for an open in the circuit. If heater circuit fuse is blown, then suspect a bad heater in the o2 sensor causing a blown heater circuit fuse. Replace sensor and fuse and recheck. b. If ground is missing, trace the circuit and clean or repair ground circuit. 4. Next, with connector still unplugged, check for 5 Volts on the reference circuit. If this 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, then there is 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 internal short. Replace PCM. ** (NOTE: on Chrysler models, a common problem is the 5Volt reference circuit can be shorted out by any sensor on the car that uses a 5 Volt reference. 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 fix the 5 Volt reference short.) 5. If all the voltages and grounds are present, then replace the Bank 1,2 O2 sensor and re-test.
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"Delete Error Code Permanently, Disable DTC Error Code Function for p0140 in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p0140 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p0140.
