- Transmission Issue: The OD (overdrive) light blinking, often indicates an issue with the transmission. When this light blinks, it means the transmission is not functioning properly and shifting into overdrive. It is advisable to have the transmission checked by a qualified mechanic or transmission specialist to diagnose and resolve the issue.
- Loss of Communication: Your Mountaineer's computer (PCM) uses a network to communicate with its sensors and other modules, including the transmission control module. If there is a break or short in the wiring, this communication will be lost and codes may set in the PCM.
- Defective Speed Sensor: The speed sensor is responsible for providing the PCM with the vehicle's speed information. If the sensor fails, the PCM may not be able to correctly control transmission shifts, leading to the OD light blinking and illuminating the service engine light.
- Wiring Harness Issues: The electrical wiring harness involved in the transmission control can also become damaged due to factors such as corrosion or wear. This can lead to signal malfunctions and trigger the blinking of the OD light, as well as other transmission-related issues.
- PCM Fault: While less common, the PCM itself may have internal issues, causing it to malfunction and incorrectly control transmission functions, including overdrive engagement. This can lead to both the OD light blinking and the service engine light turning on.
It is important to note that these are just some possible reasons, and the exact issue can only be determined with proper diagnostics. We recommend that you have the vehicle inspected by a trusted mechanic or transmission specialist who can use diagnostic tools and their knowledge to identify the underlying cause and provide necessary repairs.
