P0140 O2 Sensor Circuit No Activity Detected (B1S2)

Description and meaning of DTC p0140

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 voltageto the Oxygen sensor. When the O2 sensor reaches operating temperature, it willgenerate 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 generatesa 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-WayCatalyst (TWC) system (catalytic converter) is used to control tailpipe emissions. The PCM uses the signal received from Oxygen sensor 2 (#2 indicates aft of catalyticconverter, #1 indicates pre-converter) to read efficiency of TWC. Normally thissensor will switch between high and low voltage at a noticeably slower ratethan 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.

p0140 diagnostic trouble code 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 theMIL. The reason is this: The rear or post catalytic converter Oxygen sensordoes not affect fuel deliver(this is an exception on Chryslers). It only MONITORSthe efficiency of the catalytic converter. For this reason, you will likelynot notice any engine trouble.

DTC p0140 - possible causes

The causes for a P0140 code are fairly few. They could be any of the following:Shorted heater circuit in O2 sensor. (Usually requires replacement of heatercircuit fuse in fuse block also) Shorted signal circuit in O2 sensor Melting of harness connector or wiring due to contact with exhaust system Water intrusion in harness connector or PCM connector Bad PCM

How to fix OBD-II diagnostic trouble code p0140

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, sensor2, 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 waitfor the problem to surface before you can accurately diagnose. However, if it doesn't switch, or is stuck then perform the following: 2. Shutoff vehicle. Visually check the Bank1,2 harness connector for melting or chafingof 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 12Voltsat the Heater Circuit supply and for proper ground on the heater circuit groundcircuit. a. If 12V heater supply is missing, check the proper fuses for an openin the circuit. If heater circuit fuse is blown, then suspect a bad heater inthe o2 sensor causing a blown heater circuit fuse. Replace sensor and fuse andrecheck. b. If ground is missing, trace the circuit and clean or repair groundcircuit. 4. Next, with connector still unplugged, check for 5 Volts on the referencecircuit. If this is missing, check for 5 Volts at the PCM connector. If 5 Voltsis 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 PCMand the o2 sensor connector. However, if there is no 5 Volts present at thePCM connector, the PCM is likely at fault due to internal short. Replace PCM. ** (NOTE: on Chrysler models, a common problem is the 5Volt reference circuitcan be shorted out by any sensor on the car that uses a 5 Volt reference. Simplyunplug each sensor one at a time until the 5 Volts reappears. The last sensoryou unplugged is the shorted sensor. Replacing it should fix the 5 Volt referenceshort. ) 5. If all the voltages and grounds are present, then replace the Bank1,2 O2 sensor and re-test.

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