P0170 — Fuel Trim (Bank 1)
Moderate severityWhat it means
P0170 is stored when the engine control unit sees a fault involving the fuel trim (fuel correction) on bank 1. Fuel trim is how much the control unit adds or removes fuel to keep the air–fuel mixture correct on bank 1; this code means the correction reached its limit.
Common symptoms
- Rough idle or hesitation
- Higher fuel consumption
- Check engine light
Likely causes
- An intake/vacuum leak or a dirty MAF sensor (lean)
- A leaking injector, high fuel pressure or a faulty oxygen sensor (rich)
What to check first
- Read long- and short-term fuel trims on bank 1 in live data
- Look for intake leaks and check fuel pressure and the MAF reading
Can you keep driving?
Usually drivable, but the wrong mixture wastes fuel and can affect the catalytic converter — diagnose soon.
Frequently asked questions
What is the most common cause of P0170?
The most likely cause is: An intake/vacuum leak or a dirty MAF sensor (lean). Several other faults can set P0170 as well, so confirm the real cause with live data and the checks above before replacing any parts.
Can I just clear P0170 and keep driving?
Clearing P0170 with an OBD2 scanner turns the warning light off, but if the underlying fault has not been repaired the code will usually come back within a few drive cycles. Fix the cause first, then clear the code to confirm the repair worked.
How serious is P0170?
P0170 is a moderate-severity code. The car is often still drivable, but have it diagnosed soon — the underlying problem can get worse and it may fail an emissions test.
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