What does a defective gear indicator display lead to in an auto-shift transmission?

A defective gear indicator display in an auto-shift transmission can lead to the engine starting in any gear. This situation occurs because the gear indicator is responsible for informing the driver and the vehicle's control system of the current gear selection. When this indicator is faulty, it may not accurately reflect the actual gear position, allowing the engine to be started while in a gear other than neutral.

This can pose a significant safety risk, as starting the engine in gear could cause the vehicle to move unexpectedly, potentially leading to accidents or injuries. Therefore, ensuring the gear indicator functions properly is crucial for safe vehicle operation. The other options do not align with the consequences of having a defective gear indicator, as they focus on outcomes that would typically rely on accurate gear selection and transmission operation.