Severity and Symptoms
A P2097 code means the post-catalytic converter O2 sensor has detected a rich exhaust condition. Fuel efficiency may be compromised and the code should be considered severe.
Symptoms of a P2097 code may include:
- Decreased fuel efficiency
- Lack of overall engine performance
- Other associated diagnostic trouble codes may be stored
- Service engine soon light illumination
Possible causes of this engine code include:
- Faulty catalytic converter
- Faulty mass airflow or manifold absolute pressure sensor
- Faulty O2 sensor(s)
- Burned, chafed, broken, or disconnected wiring and/or connectors
- Engine exhaust leaks
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSBs) for your specific vehicle. Your issue may be a known problem with a known fix released by the manufacturer and can save you time and money when diagnosing.
A diagnostic scan tool, a digital volt ohm meter (DVOM), and a vehicle service manual will be helpful in diagnosing a P2097 code. AllData (DIY) is also an excellent source for system wiring diagrams and other application-specific information.
The engine must be running efficiently before attempting to diagnose this code. Misfire codes, throttle position sensor codes, manifold absolute pressure codes, and mass airflow sensor codes should be addressed before attempting to diagnose a P2097 code.
Begin with a visual inspection of the system wiring harnesses and connectors. With a P2097, I would pay particular attention to harnesses that are routed near hot exhaust pipes and manifolds, as well as those routed near sharp edges (cylinder head).
Connect the scan tool to the diagnostic port and retrieve all stored trouble codes and freeze frame data. Write this information down. This may prove helpful if this turns out to be an intermittent code. Intermittent codes can be more difficult to diagnose.
If the P2097 immediately resets, start the engine and allow it to reach normal operating temperature. Let it idle (with transmission in neutral or park). Use the scan tool to observe the O2 sensor input data. Limiting the data stream scope to include only relevant data will allow you to get a faster response. Observe the downstream O2 sensor signal. If the engine is running efficiently, the downstream O2 sensor data should reach a midpoint and settle there.
The DVOM can be used to check the resistance of the O2 sensor in question, as well as the voltage signals and grounds for the O2 sensor circuit. Disconnect associated controllers before attempting to test system circuit resistance with the DVOM.
Additional diagnostic notes:
- The downstream O2 sensor should not switch as frequently as the upstream sensors (once the PCM has entered closed loop operation). If the downstream sensor continues to switch as frequently as the upstream sensor, after the engine has warmed up and the PCM has entered closed loop operation, suspect a faulty catalytic converter
- When catalytic converter replacement is necessary, consider an OEM quality component. Rebuilt or lower quality replacement converters typically fail quickly and repeatedly