P2099 Code: Post Catalyst Fuel Trim System Too Rich (Bank 2)

Code P2099 is one of many trouble codes that may be logged and retrieved from the OBD system. Here is some basic information that may help you understand what this code may mean for your vehicle. 

What Does the P2099 Code Mean?

Diagnostic trouble code (DTC) P2099 stands for “Post Catalyst Fuel Trim System Too Rich (Bank 2).” This code may be logged when the powertrain control module (PCM) detects a biased signal voltage input from the downstream oxygen sensor for engine bank 1 that indicates a problem with the air-fuel mixture. 

The PCM recognizes changes in voltage as variations in exhaust oxygen concentration. These variations reflect whether the engine is running lean or rich. The voltage signal output from the oxygen sensor is lower when more oxygen is present in the exhaust. On the other hand, the voltage signal output is higher when less oxygen is present in the exhaust. 

This information is used by the PCM to calculate fuel delivery and ignition timing. Once the PCM enters closed loop operation, if the bank 2 downstream oxygen sensor circuit detects an air-fuel mixture that can no longer be corrected, code P2099 will be stored.

Depending on the severity of the problem, related error codes may also be stored with this DTC. Code 2099 is very similar to error code P2098.

Note: The definition of code 2099 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P2099 Code?

P2099 is a generic code, so it can have several triggers. Here are the most common:

• A faulty sensor (oxygen sensor, mass air flow sensor, etc.)
• Circuit issues, such as damaged wires or a poor connection
• Exhaust leak
• Vacuum leak
• Fuel delivery issues
• An issue with the PCM, such as software in need of an update

What are the Common Symptoms of the P2099 Code?

You may notice the following symptoms if you drive a vehicle that has set a P2099 trouble code:

• Active check engine light
• Excessive fuel consumption
• Poor engine performance

How to Diagnose the P2099 Code

If you have sufficient DIY automotive diagnostic and repair experience, you can try using a scan tool record utility to diagnose P2099.

Keep in mind that P2099 is a generic code that may be set across several makes and models. However, this does not mean that there is a one-size-fits-all approach to diagnosing its underlying cause. The steps for troubleshooting this code will vary depending on your vehicle’s make and model.

Check out this video to get an idea of what the diagnostic process for this code might involve:

How to Fix the P2099 Code

P2099 may share similar triggers and symptoms with other fault codes. However, that does not mean that they share repair steps as well. All vehicles are different, so make sure to refer to a factory repair guide that is specific to your car.

If you’re considering troubleshooting this code on your own, it’s a good idea to refresh your auto repair knowledge before attempting any fixes. Always consult the vehicle repair manual or an online repair database to learn the appropriate diagnostic and repair procedures for this code. Alternatively, you may leave this job to a professional.