P0170: Fuel Trim Malfunction (Bank 1)
Fuel trim on bank 1 is out of the range the engine computer can correct, either too rich or too lean.
Green, yellow, red: three ways P0170 can look
The same code can be a quick fix or a reason to pull over. Match your situation to the closest example.
Keep an eye on it
Drives normally.
Schedule a repair
Rough idle or returns. Diagnose soon.
Stop and get help
Misfires or flashing light. Stop driving.
Symptoms you might notice
- Rough idle
- Poor economy
- Check engine light
Common causes, cheapest first
- Vacuum leak
- MAF sensor problem
- Fuel pressure problem
- Leaking injector
What you can check before calling
- Look for related lean or rich codes
- Check for vacuum leaks
A code points to a system, not a part. Replacing parts based on the code alone is how people spend money without fixing the problem. Testing confirms the cause first.
Generic codes (second character 0) mean the same thing on every vehicle. Some manufacturers add their own details, so check service information for your exact vehicle.
More fuel & air mixture codes
Look up another code
Cummins fault code (like 1922), J1939 SPN and FMI (like SPN 3251 FMI 0), or an OBD-II code (like P0420).
Questions
What does P0170 mean?
P0170 means "Fuel Trim Malfunction (Bank 1)". Fuel trim on bank 1 is out of the range the engine computer can correct, either too rich or too lean.
Can I drive with code P0170?
It depends on what the vehicle is doing. Green: Drives normally. Yellow: Rough idle or returns. Diagnose soon. Red: Misfires or flashing light. Stop driving.
What causes P0170?
The most common causes are: vacuum leak; mAF sensor problem; fuel pressure problem.
Is P0170 a serious code?
It can be. Misfires or flashing light. Stop driving.
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