Error Code P2195 is defined as O2 Sensor Signal Stuck Lean Bank 1 Sensor 1.

This error code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.

For some vehicles like Toyotas, this code actually refers to A/F (Air/Fuel ratio) sensors, which are basically more sensitive versions of oxygen sensors.


The PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) monitors the Air/Fuel ratio of the exhaust through the O2 (oxygen) sensor, and keep things as normal as possible by keeping an air/fuel ratio of 14.7:1 through the fuel system. The oxygen A/F sensor outputs a voltage reading that the PCM uses.

Error Code P2195 means the A/F ratio has deviated from 14/7:1 and the PCM can no longer correct it by itself.  Meaning, the engine has tried to lean out a rich condition and failed.

Bank 1 is the side of the engine that contains the Cylinder #1. P2195 means the sensor between the engine and the catalytic converter (not the one behind it).

Other similar codes include:

If there are other codes present other than the P2195, always fix them in order of their appearance.

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other symptoms include:

  • Engine running rough
  • Rich condition
  • Engine misfires

Possible Causes

There are many potential causes for the A/F ratio to deviate from its specified specifications that the engine can’t correct, such as:

  • Defective Oxygen (O2) or A/F ratio sensor or sensor heater
  • Open or short in O2 sensor circuit (harness, wiring)
  • Problem with the fuel pressure or fuel injector
  • Leaks in the intake air or engine vacuum
  • Defective fuel injector(s)
  • Fuel pressure too high or too low
  • PCV system leak/fault
  • Defective A/F sensor relay
  • ECT sensor malfunction
  • MAF sensor malfunction
  • Low fuel pressure too
  • Fuel Leak
  • Air suction in air intake system
  • Defective PCM

How to Check

As with other codes, technicians diagnose this code by using a scan tool to document the codes present in the PCM and check their freeze frame data to determine when the failure has occurred.

Next, technicians check for leaks in the intake vacuum or intake hose between mass air sensor and throttle body.

Then, they check for fuel pressure.

Next, they check if the code is present on both sides or if only one side of the engine is running rich.

Lastly, they check the fuel injectors if they’re stuck open or leaking.

How to Fix

Depending on the result of the diagnosis, common repairs for this code include:

  • Replacement of the O2 sensor
  • Replacement of the fuel pressure regulator
  • Replacement of a leaking injector
  • Replacement of a cracked intake air tube
  • Cleaning or Replacement of contaminated mass airflow sensor

One of the most common mistakes when addressing this code is failing to check the air filter for damage. A damaged air filter allows air to enter the intake unmetered by the mass air sensor, which in many cases, can be the primary cause of the problem.