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P0171 OBD2 Code in 1996 Mazda B2300: Causes and Fixes for Lean Bank 1 Fuel Mixture

Model: 1996 Mazda B2300 Fault Code: P0171 Posted: 2016-07-28 17:14

I recently encountered a P0171 diagnostic trouble code on my 1996 Mazda B2300, indicating a lean condition in Bank 1. My vehicle shows consistently high short-term and long-term fuel trim values—above the ideal 14:1 air-to-fuel ratio—suggesting an overly lean mixture. I suspect that a leaky or corroded fuel hose to the gas tank could be contributing to this issue, as it may allow unburned fuel vapor to escape or disrupt proper fuel delivery. I have already replaced all relevant components including air intake hoses, fuel filter, air filter, oxygen sensors, and PCV valve. Despite these changes, the engine check light activates between 20 and 600 miles of driving. The truck runs smoothly with no signs of misfiring or poor performance. Could a deteriorated fuel hose be causing the P0171 code? What are typical fuel trim values (e.g., LTFT +15) that indicate a lean condition, and how can I verify this using an OBD2 scanner? Additional resources: https://www.obd-codes.com/p0171

Related fault codes
P0171
Comments (3)
Anonymous 2016-07-29 07:24

Yes, a leaking or corroded fuel hose to the gas tank can cause a lean condition and trigger P0171. Check fuel pressure using an accurate gauge. Monitor both short-term and long-term fuel trims—values such as LTFT +15 or GTFT +20 typically indicate a lean mixture. For more details, refer to: https://www.obd-codes.com/p0171

Anonymous 2016-07-29 15:52

My short-term fuel trim fluctuated from 10.9% to 82%, and the long-term fuel trim ranged between 23.4% and 33.5%. These values are significantly above normal, indicating a lean condition. I’ve ordered a new fuel filler hose and will monitor if this resolves the P0171 code. Thanks for the guidance, Kev.

Anonymous 2016-07-30 12:43

For more in-depth information on interpreting fuel trim values, see: https://www.obd-codes.com/faq/fuel-trims.php