Ron Ananian, The Car Doctor discusses how modern vehicles, specifically a 2020 Lexus ES 350, require more complex procedures when replacing a battery. And sometimes the customer has a hand in it, even if by accident.  After replacing the battery in this Lexus, the car developed multiple warning lights, including check engine, ABS, and traction control. Diagnosis revealed fuel trim imbalances, with a significant discrepancy between bank one (-35%) and bank two (+35%).

Upon further investigation, the issue was traced to bad fuel from a low-cost gas station. The fuel appeared murky and contained unexpected ethanol content, causing performance issues. The host emphasizes the importance of buying quality fuel from reputable stations to avoid similar problems.

Key takeaways:

1. Battery replacement is no longer straightforward—many vehicles require a reset procedure to avoid electronic malfunctions.
2. Fuel quality matters—cheap fuel can lead to engine issues, especially in modern cars with complex fuel injection systems.
3. Regular diagnostics are crucial—understanding baseline performance metrics can help identify problems early.

The segment concludes with a listener call regarding a 2014 GMC Sierra experiencing intermittent starting issues. The host suggests checking fuel trim data and vehicle grounds, emphasizing how voltage-sensitive modern vehicles can be.

The overarching theme: Cars are becoming more technologically complex, making proper diagnostics and quality maintenance more critical than ever. 

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