The P2099 diagnostic trouble code (DTC) indicates that the powertrain control module (PCM) has detected an excessively rich fuel condition in the post-catalyst exhaust on bank 2 of the engine.
This code specifically relates to the fuel trim adjustments made by the PCM based on feedback from the downstream oxygen sensor after the catalytic converter.
What Does Code P2099 Mean?
The Code 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.
Potential Causes of a P2099 Code
Several factors can contribute to the P2099 code:
- Faulty downstream oxygen sensor
- Deteriorated catalytic converter
- Leaking fuel injectors
- Malfunctioning MAF sensor
- Vacuum leaks
- Faulty fuel pressure regulator
- Contaminated engine oil
- Exhaust leaks before the downstream O2 sensor
- PCM software issues
- Wiring or connector problems in the O2 sensor circuit
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:
- Poor engine performance
- Active check engine light
- Excessive fuel consumption
How to Fix the P2099 Code?
Repairs that can fix this trouble code may include:
- Replace the mass air flow sensor
- Repair or replace circuitry for the mass air flow sensor
- Replace the manifold absolute pressure sensor or circuitry associated with it.
- Replace the fuel pressure regulator
- Replace the powertrain control module
- Replace the oxygen sensor(s) or circuitry associated with them.
- Replacing the intake tube that goes from the air cleaner to the throttle body.
How Much Does It Cost to Fix a P2099 Code?
Fixing a P2099 code can cost anywhere from $150 for a simple sensor replacement to as much as $2500 for a new catalytic converter depending on the root cause of the issue, with most repairs falling somewhere in between.
It’s often recommended that you consult a professional mechanic due to the complexity of diagnosing fuel system problems that trigger this code.