Fuel / Air · Severity: Moderate
P0172 — System Too Rich (Bank 1)
Fuel trims on bank 1 have reached the rich limit — too much fuel or too little air.
Common symptoms
- Black smoke
- Fuel smell
- Poor economy
- Rough running
Likely causes
- Leaking injector
- Faulty MAF sensor
- High fuel pressure
- Blocked air filter
- Faulty coolant temp sensor
First test to run
Check MAF reading against expected airflow at idle, then check fuel pressure and injector leak-down.
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