P0170: Fuel Trim Malfunction (Bank 1)
Can you still drive? Yes, but the engine is not running optimally. Extended driving with extreme fuel trim values can damage the catalytic converter. Diagnose and repair within a couple of weeks.
What Does P0170 Mean?
Code P0170 indicates that the fuel trim values for bank 1 have exceeded the acceptable correction range. Fuel trims represent how much the ECM is adjusting fuel delivery from its base calibration. P0170 is set when long-term fuel trims are excessively rich or lean for a sustained period, indicating the ECM can no longer adequately compensate for a fuel delivery or air metering problem.
Need to read your codes?
An OBD-II scanner lets you read and clear diagnostic trouble codes from your vehicle's computer. Most scanners work with any car made after 1996.
Browse OBD-II Scanners on AmazonCommon Causes
- Vacuum leak on bank 1 side
- Dirty or faulty mass airflow sensor
- Clogged fuel injectors
- Weak fuel pump
- Faulty oxygen sensor providing incorrect feedback
Symptoms
- Check engine light on
- Rough idle
- Hesitation on acceleration
- Poor fuel economy
- Possible engine stalling
Diagnostic Steps
- 1Read short-term and long-term fuel trim values for bank 1 with scan tool
- 2Perform smoke test for vacuum leaks on bank 1
- 3Clean or test mass airflow sensor
- 4Check fuel pressure at the fuel rail under load
- 5Test bank 1 oxygen sensors for proper switching
- 6Inspect fuel injectors for even spray pattern or blockage
Recommended Parts & Tools
mass airflow sensor
fuel injector cleaner
vacuum leak smoke machine
fuel pressure gauge
Estimated Repair Cost
| Type | Estimated Cost |
|---|---|
| Total Repair Cost Range | $100 - $800 |
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Frequently Asked Questions
What are fuel trims?
Fuel trims are percentage adjustments the ECM makes to fuel delivery. Short-term fuel trim (STFT) reacts quickly, while long-term fuel trim (LTFT) represents a learned adjustment. Values above +10% indicate lean, below -10% indicate rich.
How is P0170 different from P0171?
P0171 specifically means bank 1 is running lean (too much air or too little fuel). P0170 is a broader code indicating the fuel trim correction has gone out of range in either direction, rich or lean.
Community Fix Reports
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