P0139 Oxygen Sensor Circuit Slow Response (B1S2)

Description and meaning of DTC p0139

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. This involves the rear oxygen sensor on the driver's side. This code indicatesthe engine air fuel ratio is not being adjusted by the oxygen sensor signalor the ECM as expected to do so, or not adjusted as often as expected to doso once the engine is warmed or under normal engine use. Bank 1 is the is the bank of cylinders that contains cylinder #1.

p0139 diagnostic trouble code symptoms

You will likely not notice any drivability problems, although there may besymptoms.

DTC p0139 - possible causes

A code P0139 may mean that one or more of the following has happened:The oxygen sensor is faultyThe wiring to the sensor is broken / frayedThere is an exhaust leak

How to fix OBD-II diagnostic trouble code p0139

The simplest thing to do is to reset the code and see if it comes back. If the code comes back, the problem is more than likely the rear driver's sideoxygen sensor. You will likely wind up replacing it but you should also considerthese possible solutions:Check and fix any exhaust leaksCheck for wiring problems (shorted, frayed wires)Check the frequency and amplitude of the oxygen sensor (advanced)Check for a deteriorating / contaminated oxygen sensor, replace if necessaryCheck for inlet air leaksCheck the MAF sensor for proper operation

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