P2188 means the long-term fuel trim of bank 1 has to remove more fuel than allowed in the idle and low-load range, the additive part of the mixture adaptation on Bosch-type systems. GM's 2008 3.6 LLT sets it below -6.0 % at 520 to 1120 rpm and 1.7 to 7.8 g/s, with closed loop and coolant above 60 °C. On the Opel/GM 2.0 turbo in the Saab 9-5 (2010) the weighted long-term trim must stay below its limit for 4 s or 50 s in total (Type B); Saab's test gives -22 to 0 % as normal trim and 19 to 42 kPa manifold pressure at idle. At idle the extra fuel typically comes from sources the ECM does not meter: Mercedes lists for the M132 engine a leaking PCV valve, leaking injectors or excessive fuel pressure, wrong intake pressure readings, a restricted or worn throttle and a contaminated oxygen sensor. A saturated charcoal canister purging at idle has the same effect. Stellantis found an airflow straightener in the air box clipped in wrong, which disturbed the air mass reading and set P2188 and P2190.
Medium severity. Can I keep driving?You can reach a repair shop by driving without pushing the engine. Do not drag it out, because the rich mixture fouls the spark plugs and can overheat the catalytic converter; if there is a strong gasoline smell, stop and find the source.
Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank.
Symptoms
- Malfunction indicator lamp on
- Rough idle, fuel smell
Most likely causes
- Leaking injector or fuel pressure too high
- Fuel vapour from the purge valve or oil-diluted crankcase gases
- Air mass or manifold pressure reading wrong
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P2188 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 1: Air and fuel
- 88: Specific fault in that system
Frequently asked questions
Can I keep driving with code P2188?
You can reach a repair shop by driving without pushing the engine. Do not drag it out, because the rich mixture fouls the spark plugs and can overheat the catalytic converter; if there is a strong gasoline smell, stop and find the source.
What causes code P2188?
The most common causes are: leaking injector or fuel pressure too high; fuel vapour from the purge valve or oil-diluted crankcase gases; air mass or manifold pressure reading wrong.
Related codes
- P2190System Too Rich at Idle (Bank 2)
- P2178System Too Rich Off Idle (Bank 1)
- P0172System Too Rich Bank 1
- P2187System Too Lean at Idle (Bank 1)
Sources
- gsi.ext.gm.com: 08 GRP02 LLT Engine
- saabwisonline.com: dtc p2178 or p2188
- static.nhtsa.gov: SB 10062589 2280
- static.nhtsa.gov: MC 11021579 0001
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.