Here's why it *might* prevent starting:
* Anti-theft systems: Some anti-theft systems use the speed sensor signal as part of their authentication process. A faulty sensor might prevent the system from verifying the vehicle's identity correctly, thus preventing starting.
* Transmission control: The speed sensor is crucial for automatic transmissions. The transmission control module (TCM) might refuse to allow the engine to start if it can't get a signal from the speed sensor, as this indicates a critical safety issue.
* Engine control unit (ECU) diagnostics: A severely malfunctioning speed sensor could trigger a fault code in the ECU. Depending on the severity and the car's programming, this could lead to the car refusing to start. The ECU might be programmed to prevent starting if it suspects a critical system failure.
However, it's more likely that a faulty speed sensor will cause drivability problems *after* the car starts, such as:
* Inability to accelerate properly
* Rough shifting (automatic transmissions)
* Check engine light illumination
* Cruise control malfunction
In short: While possible, it's *less likely* a speed sensor problem is the *sole* reason a car won't start. Other issues are far more common causes of no-start conditions. If your car won't start, it's best to have a mechanic diagnose the problem to determine the root cause.
