P0172 on GMC
System Too Rich (Bank 1)
P0172 on GMC vehicles indicates system too rich (bank 1). Au7o has documented this code across 2 GMC models — most commonly on Jimmy, Terrain. 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 GMC range from $80 to $250, 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 GMC by Model
GMC Jimmy(1 issue)
- Fuel Pressure Regulator Diaphragm Leak1996-2001
The fuel pressure regulator diaphragm ruptures, allowing raw fuel to be drawn into the intake manifold through the vacuum line. Causes rich running, hard hot starts, and fuel smell. Can flood the engine with fuel.
GMC Terrain(1 issue)
- Charge Air Cooler Outlet Duct Disconnecting at the Throttle Body - Sudden Power Loss and Stall2018-2022
On 1.5L LYX-equipped Terrains the charge air cooler outlet tube can separate from the throttle body inlet. The retaining clip design does not hold the duct under boost pressure and heat cycling, so the tube pops off, dumping boost and unmetered air. GM issued Service Update N192266090 covering the charge air cooler duct disconnect at the throttle body on 2019 Malibu, Equinox and Terrain 1.5L vehicles, and the condition is further covered by field bulletins PIP5651 and 22-NA-224 across the 2018-2022 range. This is separate from the frozen-CAC condition: the cooler is fine, the connection has come apart. It is also distinct from the throttle body / TPS electrical failure already documented, because the fault is mechanical air-path separation.
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View P0172 across all makes →Frequently Asked Questions
What does P0172 mean on GMC?▼
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 GMC specifically, this code is documented across 2 models.
What causes P0172 on GMC vehicles?▼
Common causes on GMC: 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 GMC?▼
Repair costs on GMC range from $80 to $250, depending on the specific model and root cause.
Which GMC models have P0172 documented?▼
Au7o has documented P0172 on 2 GMC models: Jimmy, Terrain.