P2188 means System Too Rich at Idle (Bank 1). At idle, the computer is removing more fuel than its limit on bank 1 and still seeing a rich mixture. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P2188 means
The engine computer keeps adjusting fuel to hold the air-fuel mixture near the ideal ratio, using oxygen sensor feedback. Those adjustments are fuel trims: short-term trim reacts instantly and long-term trim learns over time. Positive numbers mean the computer is adding fuel; negative numbers mean it is taking fuel away. When long-term trim sits near the limit the computer allows, it sets a lean or rich code. On a V engine, bank 1 is the side containing cylinder 1 and bank 2 is the opposite side; inline engines only have bank 1.
P2188 symptoms
- Check engine light
- Rough idle
- Fuel smell or poor fuel economy
Common causes of P2188
- Leaking fuel injector
- High fuel pressure or a leaking pressure regulator
- Faulty coolant temperature sensor reading cold
- Fuel in the oil being drawn through the PCV system
How to diagnose P2188
- Check fuel trims at idle
- Check fuel pressure and pressure hold after shutdown
- Compare the coolant temperature reading with the real temperature
Can you drive with P2188?
Usually yes; fix soon to protect the catalytic converter.
P2188 tips
Check the oil for a fuel smell; fuel diluting the oil can be drawn through the PCV system and make the engine run rich at idle.
Will P2188 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P2188 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0172 | System Too Rich (Bank 1) |
| P2187 | System Too Lean at Idle (Bank 1) |
| P0175 | System Too Rich (Bank 2) |
Guides that help
When it is more than a sensor
Fuel trim codes are almost always fixed with a leak repair, a sensor or a fuel delivery part. If a long-running lean condition has burned a valve or piston and a compression test confirms it, compare repair against a replacement on our engines page and see engine replacement cost.
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