P2099: Post-catalyst fuel trim system too rich (bank 2)

What P2099 means

The oxygen sensor after the catalytic converter (sensor 2) also helps fine tune the fuel mixture. This code means that on bank 2 it sees a rich mixture, with too much fuel, and the ECU has reached the limit of what it can correct. It can come from the sensor itself or from more fuel going in than needed.

Most common causes

• The downstream oxygen sensor old, contaminated or reading off
• Damaged wiring or connector on that sensor
• The upstream oxygen sensor giving wrong readings
• A leaking or over-spraying injector
• Fuel pressure too high (faulty regulator)
• A very dirty air filter

Symptoms

• Engine warning light on
• Higher fuel consumption
• Smell of fuel or rotten eggs from the exhaust
• May fail the emissions test at inspection

Can you drive with P2099?

With care You can drive, but running rich for a long time wastes fuel and can damage the catalyst. Have it looked at soon.

How to check it

Use a live data reader to watch the bank 2 sensor 2 voltage: if it stays high most of the time, the mixture is rich. Also compare short and long term fuel trims, which usually read negative when running rich.

How to read and clear P2099 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P2099 with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

• P2091 Camshaft actuator B control circuit high (bank 1)
• P2096 Post-catalyst fuel trim system too lean (bank 1)
• P2097 Post-catalyst fuel trim system too rich (bank 1)
• P2098 Post-catalyst fuel trim system too lean (bank 2)
• P20B9 Reductant (AdBlue) heater A control circuit open or faulty
• P20E8 Reductant (AdBlue) pressure too low
• P20EE SCR NOx catalyst efficiency below threshold (bank 1)
• P2002 Diesel particulate filter efficiency below threshold (bank 1)
• P2003 Diesel particulate filter efficiency below threshold (bank 2)
• P2004 Intake manifold runner control stuck open (bank 1)
• P2005 Intake manifold runner control stuck open (bank 2)

P2099 is a generic code, so it means the same on any make, for example on Audi, Dacia, Fiat, Kia, Opel / Vauxhall, Toyota. See what Final OBD does on your car in makes and models.