OBD-II trouble code
P2190: System Too Rich at Idle (Bank 2)
One bank rich, only at idle. That combination clears the fuel system as a whole and points at something that adds a fixed quantity of fuel — which matters most at idle, because idle is when the engine asks for the least.
Quick facts
- System
- Powertrain
- Category
- Fuel and Air Metering
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $120 – $1,400
- DIY difficulty
- Intermediate DIY
What does P2190 mean?
The module has been removing fuel from bank 2 at idle for long enough, and at a large enough correction, that it has run out of authority. Bank 2 is the bank that does not contain cylinder number one. The mixture is still rich at the limit of what the module can subtract, so it has set a code.
Two qualifiers narrow this enormously, and taking them seriously is the difference between an afternoon and a week.
The first is that it is one bank. Anything both banks share cannot be the cause of a fault only one of them has — the intake plenum downstream of the throttle, fuel supply pressure, the fuel pump, the regulator, the purge valve, the air filter, the mass airflow sensor. All of those feed both sides equally, so a fault in any of them would have made both banks rich together. Ruling them out on that logic alone costs nothing and eliminates most of the expensive tests people start with. There is no need to hook up a fuel pressure gauge to prove a shared component innocent when the code itself has already done it.
The second qualifier is idle, and it is where the useful deduction lives. At idle the engine is burning less fuel than at any other time it is running, so any source that adds a roughly fixed amount of fuel becomes a large percentage of a small total. Pull away and the commanded quantity climbs, the same fixed addition becomes a small fraction of a big number, and the trims come back to normal. That is the mechanism behind the classic complaint — rich at a standstill, fine once moving — and it is why the code is qualified to idle rather than being a general rich code.
Put the two together and what remains is a short list of things that are specific to bank 2 and that add fuel at a fixed rate. Top of it is an injector on that bank leaking, either seeping while closed or failing to seal at rest. A leaking injector dribbles a small, steady quantity into the port, which is trivial at speed and substantial at idle — exactly the fingerprint this code describes. Next is the bank 2 upstream sensor itself reporting falsely rich, in which case the mixture is fine and the module is being told to remove fuel that was never there; a sensor causing the problem rather than reporting it. Then, on engines that have per-bank exhaust gas recirculation or crankcase ventilation feeds, an issue on the bank 2 feed only. And finally, though less common, low compression or a fouled plug on a cylinder in that bank, which lets unburnt fuel reach the sensor and reads as rich even though fuelling is correct.
The consequence worth acting on is the catalytic converter. Unburnt fuel arriving at a hot converter burns there instead of in the cylinder, and sustained rich running on one bank is the standard way to destroy the converter on that side — a repair that generally costs more than everything above it on this list combined.
Common causes
- Injector on bank 2 leaking or failing to seal at rest, adding a small fixed quantity that dominates at idle
- Bank 2 upstream oxygen sensor reporting falsely rich, causing the module to remove fuel that was never in excess
- Bank-specific EGR or crankcase ventilation feed faulty on engines that have one per bank
- Low compression or a fouled spark plug on a bank 2 cylinder allowing unburnt fuel to reach the sensor
- Bank 2 injector wiring or driver fault holding an injector open slightly longer than commanded
- Contaminated or damaged bank 2 sensor from coolant, oil or silicone, skewing its reading rich
- Exhaust leak downstream of the bank 2 sensor on some layouts, disturbing what the sensor sees
- Carbon or fuel contamination on the bank 2 sensor tip slowing its response and biasing the average
Symptoms
- Rough or uneven idle that smooths out as soon as the vehicle is moving
- Fuel smell at idle, particularly noticeable at a standstill in traffic
- Negative long-term fuel trim on bank 2 at idle while bank 1 stays near zero
- Fuel trims that return to normal off idle and drift rich again when stopping
- Black smoke from the exhaust at idle
- Fuel economy down without a strong complaint at cruising speed
- Occasional misfire on a bank 2 cylinder from a fouled plug
- Sulphur or rotten-egg smell as the converter deals with the excess fuel
Diagnostic steps
- 1.Confirm which physical bank is bank 2 on this engine before touching anything. It is the bank without cylinder number one, and getting it wrong wastes the whole diagnosis.
- 2.Use the one-bank qualifier to eliminate everything shared. The plenum, fuel pressure, the pump, the regulator, the purge valve and the airflow sensor all feed both banks, so none of them can produce a single-bank fault.
- 3.Compare fuel trims on both banks at idle and again at cruise. Confirm the divergence is real and that it closes off idle, which is what makes the fault a fixed-rate addition rather than a proportional one.
- 4.Test injector leak-down on bank 2 — pressurise the rail with the engine off and watch for pressure bleeding away, which points at an injector not sealing at rest.
- 5.Pull the plugs on bank 2 and compare them with bank 1. A wet or heavily fuel-fouled plug identifies the cylinder and often the injector.
- 6.Check the bank 2 upstream sensor's live behaviour against bank 1 on the same drive. A sensor reporting falsely rich causes this code rather than reporting it, and the fix is the sensor, not the fuel system.
- 7.On engines with per-bank EGR or crankcase ventilation feeds, inspect the bank 2 side specifically rather than testing the system as a whole.
- 8.Run a compression or relative compression test on bank 2 if the plugs or the misfire data suggest a cylinder is not burning its charge properly.
- 9.After repair, verify at idle specifically — this fault hides at cruise, so a road test at speed alone will not confirm anything.
Repair cost
$120 – $1,400
Diagnosis is $120 to $250. Replacing one leaking injector is $250 to $600 fitted, and a full bank set is $500 to $1,300 on engines where the intake has to come off. A bank 2 upstream oxygen sensor is $180 to $600 fitted depending on access. Spark plugs on one bank are $80 to $250. The figure that is not in this range is the catalytic converter — $900 to $2,500 for the bank 2 unit — which is what sustained rich running eventually costs and the reason not to leave this code alone for months.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with fuel injector replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.