Code result
P0172
System Too Rich
Moderate severity
What it means
Long-term fuel trim on bank 1 is at the lower limit — the ECU is removing fuel from baseline but mixture remains too rich. Indicates excess fuel delivery, restricted air flow, or a faulty oxygen sensor reporting falsely lean.
Is it safe to drive?
Use caution
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.
Most likely causes
Fuel pressure regulator stuck closed
highOne of the most commonly reported causes for this code — check this first.
Leaking fuel injector
mediumA plausible cause — test and verify before replacing parts.
Severely blocked air filter
mediumA plausible cause — test and verify before replacing parts.
Oxygen sensor reporting incorrectly
lowLess common, but worth ruling out after the more likely causes.
Related help
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