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What does code P2097 mean?

Code P2097 stands for post catalyst fuel trim system too rich bank 1.

An engine needs the correct amount of air and fuel to run properly. The air/fuel ratio is measured in the exhaust stream by the oxygen (O2) sensors. A ratio that has too much oxygen in it is said to be lean, whereas a ratio with too much fuel is said to be rich. Fuel trim is the adjustment the powertrain control module (PCM) makes to the mixture to maintain the desired air/fuel ratio.

On modern vehicles, there is one O2 sensor mounted upstream of the catalytic converter and one mounted downstream. These are referred to as sensor one and sensor two. O2 sensors are also distinguished by bank, which refers to the side of the engine the sensor is mounted on. Bank 1 refers to the side of the engine with the #1 cylinder, whereas bank 2 refers to the side of the engine with the #2 cylinder. Inline engines, have only one bank – bank 1.

The downstream sensor is used to detect any shift in the upstream sensor’s target operation. Code P2097 indicates the downstream bank 1 O2 sensor is registering a rich condition.

Get it diagnosed by a professional.

P2097 symptoms

Common causes for P2097

Code P2097 is typically caused by one of the following:

  • A clogged or leaking exhaust
  • A problem with the O2 sensor or its circuit

How to diagnose and repair P2097

Perform a preliminary inspection

The first step is to perform a visual inspection of the exhaust system and O2 sensors. A trained eye can look for damaged or leaking exhaust components, as well as problems with the O2 sensors such as damaged wiring. If a problem is found, the issue should be repaired and the code cleared. If nothing is discovered, the next step is to check for technical service bulletins (TSBs). TSBs are recommended diagnostic and repair procedures put out by the vehicle manufacturer. Finding a related TSB can greatly reduce diagnostic time.

Check O2 sensor operation

Oxygen sensor

The next step is to check O2 sensor operation. In most cases, a properly operating upstream O2 sensor should rapidly switch between 0.1-volt and 0.9 volts. A reading of 0.1-volts indicates a lean air/fuel mixture, whereas a reading of 0.9-volts indicates a rich mixture. The PCM continuously toggles between rich and lean. This is done to keep the engine operating at the sweet spot, called the Stoichiometric ratio.

Unlike the upstream sensor, the downstream sensor signal should not fluctuate. It should read steadily at about 0.45-volts. This is because the downstream sensor is not used for fuel control. Instead, it’s job is to monitor catalytic converter efficiency. If both the converter and O2 sensor are working properly, the exhaust should be “cleaned up” by the time it exits the converter. As a result, the downstream O2 sensor should produce a steady signal.

A professional will typically start this process by viewing the O2 sensor signals on a diagnostic scan tool.

  • To begin O2 sensor diagnosis, the technician connects a scan tool to the vehicles diagnostic port.
  • With the engine running, the O2 sensor signals are viewed in graphing mode on the scan tool.
  • The upstream sensor should produce a signal pattern that switches between 0.1-volts and 0.9-volts. On the other hand, the downstream sensor should read steadily at about 0.45-volts.

Readings that fall outside of the desired range indicate either an incorrect air/fuel ratio or a problem with the sensor or its circuit, requiring an . A downstream sensor that fluctuates as rapidly as the upstream sensor can also indicate a catalytic converter that needs replacing.

Check the exhaust system

If a visual inspection of the exhaust system doesn’t reveal anything, the next step is to check for restriction and leaks.

To check the exhaust system for restriction, a technician typically uses what’s referred to as a back-pressure gauge.

  • To begin the test, the gauge is installed in place of the upstream O2 sensor.
  • The engine is started and the gauge readings are compared to the manufacturer’s specifications.
  • A reading that’s higher than spec, indicates a restriction such as a plugged catalytic converter or collapsed exhaust pipe.

The technician might also inspect the catalytic converter directly by tapping on it with a mallet. A rattling noise indicates the coveter has come apart inside. Testing the converter inlet and outlet temperatures is another useful method. A properly operating converter should have an outlet temperature that’s about 100 degrees F hotter than the inlet.

A telltale sign of an exhaust leak is black streaks around the source of the leak. A hissing or tapping sound from the exhaust may also indicate a leak. To check for leaks, a rag can be stuffed into the tailpipe. This forces exhaust gases out of the leak location, making it easier to find. Note: This can be a dangerous procedure and should only be performed by a professional.

Other diagnostic codes related to P2097

  • P2096: Code P2097 indicates the PCM has detected a post catalyst fuel trim is too lean on bank 1
  • P2098: Code P2098 indicates the PCM has detected a post catalyst fuel trim is too lean on bank 2
  • P2099: Code P2098 indicates the PCM has detected a post catalyst fuel trim is too rich on bank 2

Code P2097 technical details

Fuel trim is a continuous monitor. Code P2097 can be set when the engine is in closed loop and the ambient temperature and altitude are within a specified range.

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