System Too Rich (Bank 1)
What it means
The engine is running with too much fuel relative to air on bank 1; the ECU has cut fuel to its limit.
Symptoms
Black smoke, poor fuel economy, rough running, fouled spark plugs.
Common causes
Leaking injector, high fuel pressure, dirty MAF, faulty oxygen sensor, or a stuck-open thermostat.
Recommended action
Check fuel pressure, the MAF reading and the oxygen sensors; inspect for leaking injectors.
Related codes
FAQ — P0172
What does code P0172 mean?
System Too Rich (Bank 1). The engine is running with too much fuel relative to air on bank 1; the ECU has cut fuel to its limit.
What are the symptoms of P0172?
Black smoke, poor fuel economy, rough running, fouled spark plugs.
What causes P0172?
Leaking injector, high fuel pressure, dirty MAF, faulty oxygen sensor, or a stuck-open thermostat.
What should I do about P0172?
Check fuel pressure, the MAF reading and the oxygen sensors; inspect for leaking injectors.
General reference based on the SAE J2012 standard. Exact causes for your vehicle may differ — when in doubt, consult a workshop.
← All OBD-II codes