OBD-II Code
P0170
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$80–$1,400
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P0170 means the bank 1 fuel-trim correction has exceeded the ECM's adaptive correction limits in either direction — short-term fuel trim (STFT) plus long-term fuel trim (LTFT) summed together has hit roughly +/-25% sustained, which the ECM flags as a fuel-trim malfunction that adaptive learning can no longer compensate for.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP0170 means the bank 1 fuel-trim correction has exceeded the ECM's adaptive correction limits in either direction — short-term fuel trim (STFT) plus…
P0170 means the bank 1 fuel-trim correction has exceeded the ECM's adaptive correction limits in either direction — short-term fuel trim (STFT) plus long-term fuel trim (LTFT) summed together has hit roughly +/-25% sustained, which the ECM flags as a fuel-trim malfunction that adaptive learning can no longer compensate for. Normal STFT/LTFT sits within +/-10% on a healthy engine in closed loop; +/-15-20% is marginal; +/-25% pegged is P0170 territory and indicates a real intake leak, fuel-delivery problem, or sensor lie that the ECM can't trim out.
Cheapest-first ladder
- scan STFT and LTFT on bank 1, note whether the trim is positive (engine running lean, ECM adding fuel) or negative (engine running rich, ECM pulling fuel); for positive trims (lean), the checklist is vacuum leak (smoke-test the intake, brake booster hose, PCV system), low fuel pressure (test at the rail — most port-injection systems need 45-60 psi key-on, gasoline direct-injection systems need 2,000-3,000 psi commanded rail pressure), or a dirty MAF sensor reading low (clean with CRC MAF cleaner and re-scan); for negative trims (rich), check for a leaking injector (do an injector balance test), a stuck-open EVAP purge valve, or a failed fuel-pressure regulator dumping rail pressure into the vacuum hose.
- Verify the upstream B1S1 O2 sensor is swinging full range 0.1-0.9V (narrow-band) or oscillating around lambda 1.0 (wideband 0.7-1.3); a lazy upstream sensor lies to the ECM and drives trims out of range.
- Expensive-misdiagnosis caveat: a single-bank trim problem on a V-engine often points to one specific intake-manifold runner gasket or one bank's injector wiring harness — never assume both banks need work on a bank-1-only code.
Vehicle-specific patterns2008-2013 Honda Accord/Odyssey/Pilot 3.5L J35 throws P0170 on bank 1 (rear bank on the transverse setup) from the well-documented intake-manifold run…
- 2008-2013Honda Accord/Odyssey/Pilot 3.5L J35 throws P0170 on bank 1 (rear bank on the transverse setup) from the well-documented intake-manifold runner gasket leak — the rear-bank runners crack at the plenum interface.
- 2004-2010Ford F-150 5.4L 3V throws P0170 from the same coil-boot carbon-tracking and stuck-plug cluster that triggers the misfire codes, plus from PCV elbow cracks dumping a vacuum leak into bank 1.
- 2007-2014Toyota Tundra/Sequoia 5.7L 3UR-FE throws P0170 from a torn intake-manifold gasket on bank 1 around 130-180k miles.
- 2008-2013BMW E70 X5/E60 5-series with the N62/N63 V8 throws P0170 from the well-known valley-pan coolant leak that also produces a misfire cluster, plus from MAF sensor contamination after a dirty intake-boot tear.
Estimated repair$80 to $1,400.
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