Why does your Suzuki Grand Vitara 2001 downshift a gear when you put on your lights?

The downshifting of your 2001 Suzuki Grand Vitara when you turn on the lights may indicate an issue with the electrical system, such as a weak battery or alternator. When the lights are activated, they draw additional power, which can cause the engine to momentarily struggle, prompting the transmission to downshift for more power. It’s also possible that the engine's load is temporarily affecting the performance, triggering the transmission to adjust accordingly. Checking the battery and alternator performance would be a good first step in diagnosing the issue.