P0170: Bank 1 fuel trim has gone out of range
Fuel trim malfunction, bank 1
Severity: Monitor
This code reports a mixture control fault rather than a failed part, and Ford and Mercedes bulletins describe a light with no stated safety concern, but check for drivability changes.
It gets more serious if:
- Inspect soon: Get it inspected soon if the engine runs rough, hesitates, stalls or loses power.
P0170 in short
P0170 means the computer cannot keep the fuel mixture on bank 1 within its limits. Common causes are an air flow sensor fault, an intake or exhaust leak, a weak injector or an oxygen sensor fault. Ford has a software fix for some 6.7L diesels. It is usually safe to drive short term.
The computer constantly corrects fuel delivery, called fuel trim. P0170 is set when the correction on bank 1 hits its limit and the mixture still cannot be kept right, lean or rich.
The code does not say which direction or which part. Mercedes lists it with an air flow circuit code, and Ford bulletins on 2015 to 2019 Super Duty diesels reprogram the computer.
Check the codes stored with it: P0171 or P0172 show whether bank 1 is lean or rich.
Most likely causes
Cause 1: Faulty or dirty air flow sensor
Supported by vehicle data- Why it ranks here
- Mercedes bulletin 29992 lists P0100 (airflow circuit) with P0170, and reference pages list the sensor.
- What would change this
- Rises if airflow readings are low or implausible at idle. Falls if they match expected values.
Cause 2: Intake or exhaust leak, or injector or oxygen sensor fault
Common general cause- Why it ranks here
- Reference pages list leaks, injectors and oxygen sensors as the usual causes of trim faults.
- What would change this
- Rises if smoke testing finds a leak or oxygen sensor readings are off. Falls if both test clean.
Cause 3: Powertrain computer software (2015 to 2019 Ford 6.7L diesel)
Supported by vehicle data- Why it ranks here
- Ford TSB 16-0134 and later bulletins cover P0170 on Super Duty diesels and say to reprogram the computer.
- What would change this
- Rises on the listed trucks if a dealer finds an update. Falls on other vehicles.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read codes and bank 1 short and long-term fuel trim. Note whether P0171 or P0172 is stored.
IfLean codes or positive trims
It meansCheck for air leaks and the airflow sensor.
IfRich codes or negative trims
It meansCheck injectors and the airflow sensor.
IfFord 6.7L Super Duty diesel
It meansAsk a dealer about the bulletin.
Points to: Powertrain computer software (2015 to 2019 Ford 6.7L diesel)
Step 2: Have the intake and exhaust smoke-tested and compare the airflow reading against specification.
Warning:Leak testing is done near hot and moving parts. Let a shop do it.
IfA leak is found
It meansFix the leak.
Points to: Intake or exhaust leak, or injector or oxygen sensor fault
IfNo leak and airflow readings are wrong
It meansAirflow sensor suspect.
Symptoms
- Check engine light
- Rough idle or poor fuel economy
- Hesitation or stalling Gets more serious: stop and have it checked.
Compare with: Rough idle with the check engine light on
How to fix
Step 1: With the engine off and cool, check intake hoses and the air filter box for cracks or loose clamps.
Step 2: Ask a dealer whether a software bulletin applies to your VIN.
Parts and cost context
- Mass airflow (MAF) sensor:Clean or test before replacing. Labour varies; get a quote.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
FordYour car
2015–2016 · F-250 Super Duty
Supported by vehicle dataFord TSB 16-0134 covers 2015 to 2016 Super Duty with the 6.7L diesel and P0170. Not verified as current.
2017–2019 · F-250 Super Duty
Supported by vehicle dataFord TSB 19-2029 covers 2017 to 2019 Super Duty with the 6.7L engine built before 9 Jan 2019. Not verified as current.
TSB 16-0134Status unverified
Illuminated MIL with P0170 on 6.7L diesel
2015–2016f-250, f-350 · issued · NHTSA 10090462
Some 2015 to 2016 Super Duty trucks with the 6.7L diesel may show the light with P0170 (fuel trim bank 1) set; Ford says to reprogram the powertrain computer.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
TSB 19-2029Status unverified
Illuminated MIL on 6.7L Super Duty built on or before 9 Jan 2019
2017–2019f-250, f-350 · issued · NHTSA 10155552
Covers 2017 to 2019 Super Duty trucks with the 6.7L engine with the light on and fuel trim and related codes, including P0170 and P2074.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Mercedes-BenzYour car
1999 · C-Class
Supported by vehicle dataMercedes bulletin 29992 lists P0100 and P0170 on the 1999 C230K. Not verified as current.
29992Status unverified
Check engine light with P0100 and P0170
1999c-class, slk-class · issued · NHTSA 606700
Covers a check engine light with air flow and fuel trim codes on 1999 C230 Kompressor and SLK230.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Related codes
P0170 questions
Does P0170 mean a lean or rich condition?
Neither on its own. Read the fuel trim values and any P0171 or P0172 stored with it.
Sources and review
- Ford TSB 16-0134: Illuminated MIL with P0170 on 6.7L diesel
- Mercedes-benz 29992: Check engine light with P0100 and P0170
- P0170 trouble code explanation
- P0170 OBD-II trouble code
- Ford TSB 19-2029: Illuminated MIL on 6.7L Super Duty built on or before 9 Jan 2019
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error