Fix P2099: Mechanic’s solutions that WORKED

The P2099: Post Catalyst Fuel Trim System Too Rich Bank 2 is triggered when the post-catalytic converter fuel trim system for bank 2 of the engine is running too rich, meaning there’s too much fuel and not enough air in the combustion mixture.

This can be caused by various factors, including malfunctioning oxygen sensors, exhaust leaks, or issues with fuel injectors. Proper diagnosis involves checking these components and ensuring that the vehicle’s software is up to date.

P2099 quick overview

Description	P2099: Post Catalyst Fuel Trim System Too Rich Bank 2
Is it serious?	This code suggests an issue with the vehicle’s fuel management system, which can lead to reduced fuel efficiency and potential long-term engine damage.
Possible causes	– Faulty or dirty oxygen sensors – Exhaust leaks, especially near sensors or catalytic converters – Malfunctioning fuel injectors, causing excessive fuel delivery – Problems with the vehicle’s catalytic converter – Engine running too rich due to a faulty mass airflow sensor or air intake issues – Software issues requiring PCM update
How to diagnose?	Inspect Oxygen Sensors: Check the function and condition of the oxygen sensors. Check for Exhaust Leaks: Look for leaks in the exhaust system, particularly around the catalytic converter and O2 sensors. Evaluate Fuel Injectors: Perform a fuel injector balance test to check for leaking or malfunctioning injectors. Inspect Catalytic Converter: Check the catalytic converter for signs of failure or blockage. Analyze Fuel Trim Data: Review the fuel trim readings to identify if the engine is running too rich. Inspect Air Intake System: Check the air intake system, including the mass airflow sensor, for proper operation. Check for Software Updates: Consult technical service bulletins and consider a PCM software update if applicable.

How to fix P2099 – learn from mechanics

I looked into P2099 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: GMC

Vehicle Information: 2010 GMC Acadia SLT 3.6L

Issue + Repair History:

• Only one code: P2099.
• Vehicle runs fine, but code returns after two months of clearing.
• No exhaust leaks found.
• O2 sensors working correctly.
• Recommendation from another shop to replace all six injectors due to GM update.

Other OBD2 Codes + Test Results:

• P2099: Post catalyst fuel trim system too rich bank 2.

Suggestions to Fix Issue:

• Use better-quality fuel, possibly with a lower ethanol content.
• Perform an injector balance test using a scanner.
• Check engine grounds if coils were previously bad/melted.
• Consider reprogramming the ECM if applicable.
• Inspect the fuel trims and take a fuel sample.
• Check for any restricted converters or off cam timing.

Final Fix:

• All injectors and spark plugs replaced.

Case #2: Chevrolet

Vehicle Information: 2011 Chevrolet Traverse LS 3.6L

Issue + Repair History:

• Persistent code P2099.
• Injectors cleaned, exhaust checked, no leaks found.
• Intake manifold vacuum test and fuel trim checked, all within normal limits.
• O2 sensors and MAF sensor readings normal.
• Vehicle runs well despite the code.

Other OBD2 Codes + Test Results:

• P2099 – Post catalyst fuel trim system too rich bank 2.

Suggestions to Fix Issue:

• Use high-quality fuel, possibly with lower ethanol content.
• Perform injector balance test using a scanner.
• Check for potential exhaust leaks using a smoke machine.
• Evaluate fuel trims and take a fuel sample.
• Check freeze frame data when the code sets.
• Consider performing an ECM reflash if available.

Final Fix:

• Replaced with OEM O2 sensors which resolved the issue. No codes flagged for two months post-repair.

Case #3: Jaguar

Vehicle Information: 2009 Jaguar XF Premium Luxury 4.2L

Issue + Repair History:

• Initially had codes P0051 (O2 B2 S1 heater) and P0101 (mass air).
• Replaced B2 S1 O2 sensor; afterwards, P2099 code appeared.
• Smoke test on intake showed minor leak from EGR valve.

Other OBD2 Codes + Test Results:

• P2099 – Post catalyst fuel trim system too rich bank 2.
• P0101 – Mass or Volume Air Flow “A” Circuit Range/Performance.

Suggestions to Fix Issue:

• Check for intake leaks, particularly around bank 2 or where smoke was seen near the EGR valve.
• Consider replacing spark plugs and coils if not functioning optimally.
• Swap O2 sensors from side to side to determine if issue follows the sensor.
• Repair any identified air leaks and address issues with MAF sensor.
• Clean or replace MAF sensor, especially if the sensor wire is dirty.
• Consider potential ECM issues as a last resort.

Final Fix:

• Replaced mass airflow sensor, cleared codes, and no MIL after about a week of driving. Resolving the P0101 MAF issue likely also addressed the P2099 code.

Case #4: Chevrolet

Vehicle Information: 2017 Chevrolet Silverado 1500 LT 5.3L

Issue + Repair History:

• Issue: Codes P2097 and P2099 returning after approximately 50 miles.
• Checks done: Intake for vacuum leaks, MAF performance, intake tract, fuel system pressure, injector performance, fuel in oil contamination, oxygen sensor operation, exhaust for leaks, fuel trim, catalytic converter, and evap system operation.

Other OBD2 Codes + Test Results:

• P2097: Post Catalyst Fuel Trim System High Limit Bank 1
• P2099: Post Catalyst Fuel Trim System High Limit Bank 2

Suggestions to Fix Issue:

• Check for exhaust leaks, particularly in the pre-cat area.
• Consider checking for backpressure in the exhaust system.
• Evaluate the performance and condition of fuel injectors.
• Assess the condition of the high and low-pressure fuel pumps.
• Consult factory information for potential updates, TSBs, or PIs.
• Clean the throttle bore thoroughly, beyond what a top engine cleaner might achieve.
• Look into possible ECM programming updates as a solution.

Final Fix:

• After checking pre-cat backpressure and ensuring it was okay, and assessing the in-tank fuel pump supply, an attempted PCM update was made, followed by a thorough cleaning of the throttle body. The vehicle was then driven for over 100 miles without codes resetting, suggesting the insufficiently cleaned throttle body was the primary issue.

Case #5: Land Rover

Vehicle Information: 2006 Land Rover Range Rover Sport Supercharged 4.2L

Issue + Repair History:

• Initial issue: Code P0170
• Actions taken: Checked for vacuum leaks, installed new mass air flow sensor and air filter, cleaned intake, reset PCM.
• Problem persisted after 3 miles of driving, despite fuel pressure and fuel trim being within specifications.

Other OBD2 Codes + Test Results:

• P0170 – Fuel trim malfunction

Suggestions to Fix Issue:

• Check for intake leaks or faulty oxygen sensors.
• Review Technical Service Bulletins (TSBs) for any known issues or PCM software updates.
• Consider checking the software level in the PCM and updating if necessary.
• Run an injector cleaner to address potential fuel injector issues.
• Inspect gaskets between the supercharger and the intercoolers.
• Check the oval boot connecting the intake over the valve covers for leaks under boost.

Final Fix:

• Replaced the Mass Air Flow Sensor again with a new unit from the dealer.
• After replacement and resetting the PCM, drove the vehicle for nearly 100 miles with no recurrence of codes.
• Resolving the issue seemed to be linked to the replacement of the Mass Air Flow Sensor with a functioning OEM part.

Don’t forget that you have to inspect correct components for Bank 2, If you don’t have P2097 for Bank 1 as well.

Advice	Description of Diagnostic Step
Check for Exhaust Leaks	Inspect the exhaust system for leaks, particularly at flex sections and pre-catalytic converter. Use methods like soapy water and air pressure.
Perform Injector Tests	Conduct injector balance tests or use an AFIT tool to evaluate individual injector performance for irregularities.
Inspect Fuel Quality	Assess the quality of fuel, check for high ethanol content, and consider using higher quality or recommended fuel.
Check for Intake Leaks	Utilize a smoke machine or other methods to detect any leaks in the intake system.
Evaluate O2 Sensor Function	Inspect the operation of oxygen sensors and consider swapping sensors from side to side to diagnose issues.
Inspect Throttle Body and Clean	Clean the throttle body thoroughly and recheck idle airflow compensation.
Review Technical Service Bulletins (TSBs)	Look up any TSBs or manufacturer bulletins related to the specific vehicle model for known issues or updates.
Consider PCM Update	Check for and perform any necessary PCM software updates to address potential algorithm issues.