P0170 means the fuel trim values on bank 1 have exceeded the normal correction range. The ECU can no longer properly compensate for a rich or lean condition by adjusting fuel delivery. This indicates a persistent air-fuel mixture problem that needs investigation.
DTC/P0170·Ford
P0170 on Ford: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Ford
P0170 on a Ford means the fuel trim values on bank 1 have exceeded the normal correction range. The ECU can no longer properly compensate for a rich or lean condition by adjusting fuel delivery. This indicates a persistent air-fuel mixture problem that needs investigation.
Repair cost on Ford€20 - €500
What does P0170 mean on a Ford?
Ford Focus
2005-2024The 1.6 Ti-VCT and 2.0 GDI petrol engines can trigger P0170 from vacuum leaks at the intake manifold or PCV hoses. The 1.0 EcoBoost is sensitive to MAF sensor contamination from aftermarket air filters. Always use a genuine or high-quality replacement MAF.
What causes P0170 on a Ford?
Beyond the generic causes listed on the main P0170 page, these are the Ford-specific patterns we see most often:
Ford FocusVacuum leak at intake manifold on 1.6 Ti-VCT
Ford FocusMAF contamination on 1.0 EcoBoost from oiled aftermarket filters
How to diagnose P0170 on a Ford with OBD2
Follow these steps to pinpoint the root cause of P0170:
- Use a scan tool to read short-term and long-term fuel trims for bank 1. Values beyond +/- 25% indicate a significant air-fuel ratio problem. Positive trims mean lean, negative trims mean rich
- If fuel trims are positive (lean), perform a smoke test or propane enrichment test to find vacuum leaks. Check intake manifold gaskets, PCV hoses, brake booster line, and all vacuum connections
- Inspect and clean the MAF sensor with dedicated MAF cleaner spray. A contaminated MAF underreports airflow, causing lean fuel trims
- Check fuel pressure with a gauge. Low pressure causes lean trims, high pressure causes rich trims. Compare to manufacturer specifications
- Monitor the upstream O2 sensor data. If it is sluggish or stuck, it may be providing incorrect feedback that forces the fuel trims out of range
- If trims are negative (rich), check for leaking injectors by performing a fuel injector balance test or checking for fuel smell in the oil
How much does P0170 cost to fix on a Ford? (EUR)
Estimated repair costs on a Ford (Ford costs align with the average for this code across makes).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0170 on Ford
These codes commonly cluster with P0170 on Ford vehicles:
FAQ: P0170 on Ford
What does P0170 mean?
P0170 means the engine computer has detected that its fuel mixture corrections on bank 1 have gone beyond the normal operating range. The system tries to maintain the ideal 14.7:1 air-fuel ratio by adjusting fuel delivery, but something is preventing it from doing so.
What is the difference between P0170 and P0171?
P0170 indicates a general fuel trim malfunction - the trims are out of range in either direction. P0171 specifically means the system is too lean (too much air or too little fuel). P0170 is a broader code that can indicate either lean or rich conditions.
Can a dirty MAF sensor cause P0170?
Yes. A contaminated MAF sensor underreports the amount of air entering the engine, causing the ECU to deliver too little fuel. The O2 sensor detects the resulting lean condition and the fuel trims increase to compensate, eventually triggering P0170.
How do I read fuel trim data?
Use an OBD2 scan tool to view Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT). Values near 0% are ideal. Positive values mean the ECU is adding fuel (lean correction). Negative values mean it is removing fuel (rich correction). Beyond +/- 10% warrants investigation.
Looking for the full P0170 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0170 guideSkanyx · Ford
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