P0173
Generic (SAE) Basic entry
Fuel Trim
Severity
Medium
Typical repair cost
60 – 500 EUR
System
Powertrain
What it means
P0173 is defined as "Fuel Trim". the engine control module stores it when the monitored condition for this component or system is outside the limits programmed by the manufacturer.
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Symptoms
- Check engine light on
- Rough or unstable idle
- Hesitation or poor acceleration
- Increased fuel consumption
- Possible limp mode with reduced power
Common causes
- Fuel Trim worn, contaminated or out of calibration
- Mechanical problem in the system the sensor measures
- Air, vacuum or exhaust leak influencing the reading
- Wrong or low-quality replacement part
- Wiring resistance causing a small voltage offset
How to diagnose
- Compare the live Fuel Trim reading with a known-good value or a second sensor at idle and at 2500 rpm
- Check for air, vacuum or exhaust leaks that could skew the reading
- Inspect the component for contamination and clean it if the design allows
- Verify the part number is correct for the engine
- Replace the Fuel Trim if the reading remains out of specification
Frequently asked questions
Can I keep driving with P0173?
Usually yes for a short time, but expect reduced performance or higher fuel use. Have it diagnosed within a few days.
Will clearing P0173 fix it?
No. Clearing only erases the stored code; it returns as soon as the monitor runs again unless the cause is repaired.