* Faulty Body Control Module (BCM): This module controls many functions, including the door locks and potentially communication with the transmission control module (TCM). A malfunctioning BCM could disrupt signals to these systems.
* Faulty Transmission Control Module (TCM): The TCM is responsible for gear selection. Its failure could cause the transmission to get stuck in 2nd gear and also impact communication with other modules, leading to speedometer failure.
* Problems with the vehicle's electrical system: A short circuit, blown fuse (particularly a large fuse related to power distribution), or a problem with the vehicle's wiring harness could disrupt power and communication to multiple systems.
* Faulty Speed Sensor: While less likely to cause all three problems simultaneously, a faulty speed sensor provides data to both the speedometer and the transmission, so a failure could affect both.
* Low Battery Voltage: An extremely low battery could lead to malfunctions in various electronic systems.
Do NOT drive the vehicle. Continuing to drive with the transmission stuck in 2nd gear could cause serious damage to the transmission, engine, or other components. This needs to be professionally diagnosed and repaired immediately.
You should:
1. Have the vehicle towed to a qualified mechanic or dealership.
2. Describe the problem precisely as you did here to the mechanic. The simultaneous failure of these systems is crucial information.
Attempting to fix this yourself is highly discouraged, as incorrect troubleshooting could lead to further damage and safety hazards. A proper diagnostic scan is necessary to pinpoint the exact cause.
