Hi, this is Bo, an auto expert on RepairPal's Car Genius team! Long-term fuel trim values of -10% on your 2008 Chevrolet Silverado 1500 indicate that the engine is compensating for a lean condition, meaning it's injecting less fuel than the engine control module (ECM) thinks it needs. In general, negative fuel trim values suggest that the system is trying to reduce fuel delivery, but it’s not necessarily a cause for alarm as long as the values aren’t extreme.
With Bank 1 at -6% and Bank 2 at -10%, it sounds like your engine is compensating to maintain the ideal air-fuel ratio. However, if the trims have been consistently negative for a few months, it may be worth investigating further. Here are a few things to consider:
1. **Vacuum Leaks**: A vacuum leak can lead to a lean condition, prompting the ECM to reduce fuel.
2. **Fuel Injectors**: Check if your fuel injectors are delivering the correct amount of fuel. If they’re clogged or malfunctioning, it could affect fuel delivery.
3. **Oxygen Sensors**: A faulty O2 sensor could misreport the air-fuel mixture, affecting trim values.
If you haven’t done so already, consider running a diagnostic check to see if there are any additional codes or issues that might be contributing to the negative trim values.
If you need any further advice or want help finding a trusted RepairPal shop in your area, please feel free to call us at 877-913-1554.
