P0172 on Chevrolet
System Too Rich (Bank 1)
P0172 on Chevrolet vehicles indicates system too rich (bank 1). Au7o has documented this code across 1 Chevrolet model — most commonly on Blazer. P0172 means the engine computer has determined the air/fuel mixture on bank 1 is too rich — there is too much fuel relative to air. The PCM watches the oxygen sensors and fuel trims; when it must repeatedly cut back fuel to compensate for an over-rich condition and hits its correction limit, it sets this code. Bank 1 is the side of the engine containing cylinder number one. You may notice poor fuel economy, rough idle, a sulfur/rotten-egg smell, black exhaust smoke, or fouled spark plugs. Typical repair costs on Chevrolet range from $500 to $1,200, depending on the specific model and root cause.
Common Causes of P0172
- •Dirty or faulty mass airflow (MAF) sensor
- •Leaking or stuck fuel injector
- •High fuel pressure (faulty regulator)
- •Faulty oxygen sensor giving skewed readings
- •Clogged or dirty air filter
- •Leaking evaporative purge valve adding fuel vapor
- •Engine coolant temperature sensor reading too cold
- •Worn spark plugs causing inefficient combustion
P0172 on Chevrolet by Model
Chevrolet Blazer(1 issue)
- 4.3L V6 CPI/CSFI "Spider" Fuel Injector Leaks and Poppet Valve Failure1992-2002
The 4.3L Vortec V6 used a Central Port Injection system (CPI 1992-1995, CSFI 1996-2002) with a central injector body and six plastic poppet lines — the "spider" — mounted inside the intake manifold. The plastic lines and nut-kit connections crack and leak raw fuel into the plenum, while deposit buildup sticks the poppet valves open or closed, mis-fueling individual cylinders. The result is hard hot starts, persistent misfires, fuel-pressure leak-down, and a rich/fuel-smell condition; GM addressed sticking poppets in TSB 00-06-04-003B by back-servicing the CSFI unit with a redesigned MFI assembly.
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View P0172 across all makes →Frequently Asked Questions
What does P0172 mean on Chevrolet?▼
P0172 stands for "System Too Rich (Bank 1)." P0172 means the engine computer has determined the air/fuel mixture on bank 1 is too rich — there is too much fuel relative to air. The PCM watches the oxygen sensors and fuel trims; when it must repeatedly cut back fuel to compensate for an over-rich condition and hits its correction limit, it sets this code. Bank 1 is the side of the engine containing cylinder number one. You may notice poor fuel economy, rough idle, a sulfur/rotten-egg smell, black exhaust smoke, or fouled spark plugs. On Chevrolet specifically, this code is documented across 1 model.
What causes P0172 on Chevrolet vehicles?▼
Common causes on Chevrolet: Dirty or faulty mass airflow (MAF) sensor, Leaking or stuck fuel injector, High fuel pressure (faulty regulator), Faulty oxygen sensor giving skewed readings, Clogged or dirty air filter. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0172 on a Chevrolet?▼
Repair costs on Chevrolet range from $500 to $1,200, depending on the specific model and root cause.
Which Chevrolet models have P0172 documented?▼
Au7o has documented P0172 on 1 Chevrolet model: Blazer.