P0170: Fuel trim out of limits (bank 1)
The ECU is having to correct the bank 1 mixture so much that it has reached its limit. Usually an air leak, the air flow meter or fuel supply.
| Code | P0170 |
|---|---|
| System | Engine and transmission |
| Group | P01xx, Air and fuel metering |
| Type | Generic: it means the same on every make |
| Can you keep driving? | With care |
What P0170 means
The ECU constantly adjusts the amount of fuel based on the oxygen sensor reading; this correction is called fuel trim. This code means the correction on bank 1 has gone to an extreme, without saying whether the mixture is lean or rich. On inline engines, bank 1 is the whole engine.
Most common causes
- Air leak from a vacuum hose, the intake hose or the manifold gasket
- Dirty or faulty air flow meter misreading the air
- Exhaust leak ahead of the oxygen sensor
- Wrong fuel pressure from the filter, pump or regulator
- Dirty or leaking injectors
- Upstream oxygen sensor giving false readings
Symptoms
- Engine warning light on
- Higher fuel consumption than usual
- Rough idle or hesitation
- Lack of power or harder starting
Can you drive with P0170?
With care You can drive, but with the mixture out of step the engine uses more fuel and, if left, it can damage the catalytic converter. Have it checked soon.
Open the bonnetthe in-depth explanation
How to check it
Watch the short and long term fuel trims for bank 1 in live data. Large positive values mean too little fuel or too much air; large negative values mean the opposite. Noting whether they change between idle and higher revs is very helpful for the garage.
How to read and clear P0170 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0170 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P016C Mixture control has reached its limit and the mixture is still too lean
- P016D Fuel pressure control takes too long to enter closed loop operation
- P016E The closed loop fuel pressure control in the limit pressure gives a higher
- P016F The closed loop fuel pressure control in the limit pressure gives a lower
- P0171 Mixture too lean (bank 1)
- P0172 System running too rich (bank 1)
- P0173 Fuel trim malfunction (bank 2)
- P0174 System running too lean (bank 2)
- P0100 Mass or volume air flow sensor circuit fault
- P0101 Air flow sensor range or performance problem
- P0102 Air flow sensor circuit low input
- P0103 Air flow sensor circuit high input
What does code P0170 mean?
The ECU constantly adjusts the amount of fuel based on the oxygen sensor reading; this correction is called fuel trim. This code means the correction on bank 1 has gone to an extreme, without saying whether the mixture is lean or rich. On inline engines, bank 1 is the whole engine.
Can you drive with P0170?
You can drive, but with the mixture out of step the engine uses more fuel and, if left, it can damage the catalytic converter. Have it checked soon.
How do you clear P0170?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0170 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
