Fault code P2097 – post catalyst fuel trim system too rich (Bank 1)

Fault code P2097 is called “Post Catalyst Fuel Trim System Too Rich (Bank 1)” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P2097

When code P2097 occurs, the system detects a rich mixture condition. That is, there is too much fuel and not enough air, which the PCM has recognized by the signals from the oxygen sensors. This problem is detected after fuel correction by the oxygen sensor O₂ located after the catalytic converter Bank 1.

Fault code P2097 – post catalyst fuel trim system too rich (Bank 1)

Oxygen sensors O₂ signal the engine control computer about the amount of oxygen present in the exhaust. This is used to determine and control the fuel ratio.

The higher the oxygen content, the poorer the fuel mixture, and vice versa, the richer the mixture with less O₂. At the tip of the sensor is zirconium, which reacts to oxygen by generating its own voltage.

In order to work properly, the oxygen sensor O₂ should have a temperature of about 120°C and produce up to 0.8 volts, depending on the fuel-air balance. With a perfect mixture, the signal from the sensor should show about 0.45 volts. And the fuel-to-air ratio is 1:14.7.

The oxygen sensors not only indicate unburned oxygen in the exhaust, but also report the condition of the catalytic converter. The front sensor signals the mixture entering the converter, and the rear sensor signals the mixture leaving the converter.

When the O₂ sensors and the converter are operating normally, the front sensor reading will be higher than the rear sensor, indicating a faulty converter. If the front sensor and the rear sensor readings are the same. Then the oxygen sensor has failed, the transducer is clogged, or another component is causing an erroneous signal.

If the sensor circuit inputs O₂ after the catalyst reflect too few oxygen molecules in the exhaust. Once the PCM goes into closed-loop mode, code P2097 will be stored. Also, the malfunction indicator lamp may illuminate.

Symptoms of vehicle malfunctions

The main signal that an error P2097 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
  2. Other related fault codes may also be present.
  3. Increased emissions of harmful substances in the exhaust gases.
  4. Poor acceleration.
  5. Increased fuel consumption.
  6. Reduced engine power output.
  7. Floating revolutions, as well as attempts to stall when idling.
  8. Sometimes there may be no symptoms, despite the stored fault code.

This error is considered moderate if there are no symptoms. But if symptoms are present, the cause of error P2097 should be corrected as soon as possible. Ignoring it can cause serious damage to the catalytic converter.

Factors that can cause this error code

The error code P2097 can mean that one or more of the following problems have occurred:

  • Damaged or faulty oxygen sensor (O₂).
  • Damaged or incorrectly connected oxygen sensor wiring (HO₂S).
  • Damaged or leaking exhaust manifold, catalytic converter, muffler, exhaust pipe.
  • Delayed ignition timing.
  • Oxygen sensors at front and rear of catalytic converter are reporting too similar readings.
  • Sometimes the cause is a faulty PCM module.

How to fix or reset OBD-2 code P2097

Some suggested steps for troubleshooting and fix the error code P2097:

  1. Read all the error codes stored in the vehicle’s PCM memory with an OBD-II scan tool.
  2. Check the operation of the oxygen sensor O₂ located behind the catalytic converter (at the exhaust outlet). Voltage reading of this sensor should be stable.
  3. Diagnose other error codes that may have caused code P2097.
  4. Troubleshoot engine cylinder ignition timing and fuel system malfunctions.
  5. Inspect the oxygen sensor installed behind the catalytic converter (at the exhaust outlet) for wear and damage.
  6. Test-drive the vehicle to check the oxygen sensor.
  7. Replace or reprogram faulty PCM if necessary.

Diagnose and repair of problems

If there are no additional errors, clear fault code P2097 and perform a short test drive. To allow the PCM to go into closed loop mode, then scan the system again and see if the code has returned.

Check the catalytic converter and leaks

Check for exhaust leaks, repair them if necessary. Inspect any electrical connections that are connected to the oxygen sensor. Sometimes the electrical connector may disconnect due to heat and vibration, and the engine error indicator light will come on.

If a code is found, check the operation of the oxygen sensors to make sure they are working properly. Compare the displayed output signals with the values indicated in the manual.

Test the temperature sensor, inspect the wiring harness

Check the wiring harness that goes to the O₂ sensor. It is important to make sure there are no burned out, frayed, or severely loose spots. Which may hit any moving component while the car is in motion.

Check the operation of the oxygen sensor O₂ by thoroughly warming up the engine. Remember that the sensor will work only after it has reached its operating temperature.

Connect the sensor output to a multimeter and start the engine at about 2000-2500 rpm. The output should show a voltage fluctuating between 0.1 and 0.9 V. If the sensor output does not change or the response time is too long. This means you have a bad sensor, you should replace it.

Replacing the sensors will most likely correct the error. But sometimes, you need to replace the catalytic converter to fix the problem. If code P2097 is combined with other codes, try fixing the other codes first.

On which vehicles does this problem occur most frequently

Fault code P2097 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Cadillac (ATS)
  • Chevrolet (Cruze, Malibu, Traverse)
  • Chrysler (300C, 300M, Town and Country)
  • Citroen (C4)
  • Dodge (Caravan)
  • Ford (F-150, Mondeo)
  • GMC (Acadia)
  • Honda (Civic)
  • Hyundai (Elantra)
  • Jeep (Grand Cherokee)
  • Kia
  • Mazda (3, 6)
  • Mercedes-Benz
  • Mini (Cooper)
  • Nissan (Altima, Sentra)
  • Opel
  • Peugeot
  • Saturn (VUE)
  • Skoda (Fabia, Octavia)
  • Subaru (Outback)
  • Toyota
  • Volkswagen (Polo)
  • Volvo

Fault code P2097 can sometimes be found with other errors. The most common are the following: P0031, P0442, P2099, P2177.


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