P2178 on Buick
System Too Rich Off Idle (Bank 1)
P2178 on Buick vehicles indicates system too rich off idle (bank 1). Au7o has documented this code across 1 Buick model — most commonly on Enclave. The PCM detected that bank 1 is running rich (too much fuel relative to air) during off-idle/cruise conditions, with fuel trims pulling fuel out. A rich condition under load that fuel trim cannot fully correct.
Common Causes of P2178
- •Leaking/dripping fuel injectors
- •High fuel pressure / faulty regulator
- •Dirty/contaminated MAF sensor
- •Faulty upstream O2 sensor
- •Restricted air intake
P2178 on Buick by Model
Buick Enclave(1 issue)
- Cold-Weather PCV Deposits Can Cause Reduced Power (PI0746)2008-2011
GM PI0746 covers 2008-2011 Buick Enclave vehicles with the 3.6L LY7 or LLT engine. After a cold start or low-ambient-temperature driving, condensation can freeze at the throttle-body base while engine vapors, fuel dilution and oil mist collect in the air-inlet duct. The condition can illuminate the MIL and cause poor performance or reduced acceleration.
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View P2178 across all makes →Frequently Asked Questions
What does P2178 mean on Buick?▼
P2178 stands for "System Too Rich Off Idle (Bank 1)." The PCM detected that bank 1 is running rich (too much fuel relative to air) during off-idle/cruise conditions, with fuel trims pulling fuel out. A rich condition under load that fuel trim cannot fully correct. On Buick specifically, this code is documented across 1 model.
What causes P2178 on Buick vehicles?▼
Common causes on Buick: Leaking/dripping fuel injectors, High fuel pressure / faulty regulator, Dirty/contaminated MAF sensor, Faulty upstream O2 sensor, Restricted air intake. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P2178 on a Buick?▼
Repair costs vary widely depending on the root cause and specific Buick model.
Which Buick models have P2178 documented?▼
Au7o has documented P2178 on 1 Buick model: Enclave.