P0172 on Audi
System Too Rich (Bank 1)
P0172 on Audi vehicles indicates system too rich (bank 1). Au7o has documented this code across 1 Audi model — most commonly on S8. 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.
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 Audi by Model
Audi S8(1 issue)
- 2013-2018 S8 Warm-Soak Long-Crank or No-Start - Fuel Diagnosis Required2013-2018
Audi TSB 2046724/5 covers sporadic warm-engine no-start or long cranking after the vehicle sits without fully cooling. A rich-mixture DTC may occur, but often there is no DTC. Audi’s procedure distinguishes fuel in the oil from a short-trip profile, ECM software, high-pressure injector leakage and high-pressure fuel-pump leakage rather than assuming one failed component.
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View P0172 across all makes →Frequently Asked Questions
What does P0172 mean on Audi?▼
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 Audi specifically, this code is documented across 1 model.
What causes P0172 on Audi vehicles?▼
Common causes on Audi: 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 Audi?▼
Repair costs vary widely depending on the root cause and specific Audi model.
Which Audi models have P0172 documented?▼
Au7o has documented P0172 on 1 Audi model: S8.