P0172 on Chevrolet
System Too Rich (Bank 1)
P0172 on Chevrolet vehicles indicates system too rich (bank 1). Au7o has documented this code across 2 Chevrolet models — most commonly on Suburban, Tahoe. 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 $350 to $1,100, 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 Suburban(1 issue)
- 5.7L Vortec CSFI 'Spider' Poppet Injector Failure1996-2000
GMT400-era Vortec V8s use a Central Sequential Fuel Injection (CSFI) 'spider' assembly with poppet-valve nozzles inside the intake. The poppet valves clog with carbon or the nozzle seats fail, so they leak/dribble fuel instead of atomizing. This causes hard starting, misfires, rough idle, hesitation, poor fuel economy, and often a raw-gasoline smell; failing poppets can dump fuel into a cylinder. A very high-demand repair for high-mileage 1996-2000 Suburbans.
Chevrolet Tahoe(2 issues)
- CSFI 'Spider' Central Port Injector / Poppet Valve Failure (5.7L Vortec)1996-2000
The 1996-2000 5.7L Vortec (L31) uses a Central Sequential Fuel Injection (CSFI) 'spider' assembly: one central housing feeds six nylon poppet spray nozzles via tubes. The poppet valves gum up with carbon and either stick open (raw fuel dumps, rich condition, hard hot/cold starting, fuel smell) or the plastic tubes crack/leak causing a lean misfire. This is one of the defining driveability failures of the GMT400 Tahoe. GM issued bulletin 87-65-07 and later covered many trucks under an extended emissions warranty for the poppet nozzles.
- CSFI "spider" poppet fuel injector failure (special coverage 99066F)1996-1999
The 5.7L, 5.0L and 4.3L Vortec engines used a Central Sequential Fuel Injection (CSFI) "spider" assembly with nylon fuel tubes ending in spring-loaded poppet nozzles inside the intake. The poppets clog with carbon or leak/stick open, causing raw fuel intrusion, hard starting/flooding, and misfires. GM acknowledged the problem with special coverage 99066F on 1996-2003 CSFI systems (emissions-related, extending injector warranty to 10 years/200,000 miles for cleaning or replacement).
Looking for P0172 on a different make?
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 2 models.
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 $350 to $1,100, depending on the specific model and root cause.
Which Chevrolet models have P0172 documented?▼
Au7o has documented P0172 on 2 Chevrolet models: Suburban, Tahoe.