P0170
- Powertrain
- Generic (SAE)
- Emissions
Diagnose soon
Usually safe to drive short distances, but the fault will not clear itself and can worsen or fail an emissions test.
Fuel Trim Malfunction (Bank 1)
This code is in our catalogue but has not yet been through editorial review, so the guidance below is limited to what our structured data supports. We publish deeper diagnostic content only after a code has been reviewed — here is why.
The ECU detects that short-term and long-term fuel trim values on bank 1 are outside acceptable limits. Engine cannot maintain stoichiometric mixture — typically a vacuum leak, fuel pressure issue, or failing MAF/O2 sensor.
A trouble code records what a control module measured. It does not identify which part failed. Test before replacing anything.
- Safe to drive
- Usually safe to drive short distances, but the fault will not clear itself and can worsen or fail an emissions test.
- Urgency
- Diagnose soon
- Will it pass emissions
- No
- Check engine light
- Solid
- Clearing the light
- A completed drive cycle is normally required before the monitor re-runs and the light can clear.
| # | Cause | How often | Component |
|---|---|---|---|
| 1 | Vacuum leak (intake gasket, hose, PCV) | Very common | — |
| 2 | Fuel pressure too low or too high | Common | — |
| 3 | MAF sensor reading drifted | Common | — |
Ordering reflects how often each cause is responsible in general, not a probability for your vehicle. Confirm by testing.
- Mass Air Flow (MAF) Sensor
- Intake System
- Fuel Pressure Regulator
- Oxygen Sensor B1s1
- Definition
- Generic code set (SAE J2012 / ISO 15031-6) via the OBDexopen database, dedicated to the public domain under CC0-1.0.
- Diagnostic guidance
- Written and reviewed in-house. See our editorial policy.
- Review status
- Awaiting review
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