What are the reasons for the transmission failure warning in the Focus?

[Darren]

Here are the specific explanations regarding the causes of transmission failure in the Focus: Contamination inside the transmission: The automatic transmission failure is not caused by damage to the internal valve body, but by stubborn dirt and impurities inside, especially when these contaminants accumulate in the valve body, forming blockages that prevent effective regulation of oil pressure, leading to issues like jerking, impact, and slippage. High temperature damaging the transmission: High temperatures can degrade the quality and frictional characteristics of the automatic transmission fluid, increasing friction and wear. At the same time, sludge builds up inside the transmission, causing jerking and impact. If the temperature exceeds 120°C, rubber sealing materials begin to harden, eventually leading to leaks and reduced hydraulic pressure. If the temperature rises even higher, the transmission starts to slip, and this slippage further increases the temperature.

[McMila]

I've been driving a Focus for several years. The most common reason for the transmission warning light to come on is that the transmission fluid is too low or too dirty. Poor oil quality affects lubrication, triggering the system's automatic alarm. Sensor issues, such as a malfunctioning speed sensor, can also falsely trigger the warning, especially in older cars with high mileage. Loose wiring or corroded connectors can turn minor issues into major problems. Mechanical parts like worn dual-clutch friction plates are common in frequent stop-and-go driving. I recommend using a diagnostic tool to accurately locate the fault code first, rather than rushing to drive long distances, to avoid exacerbating the damage. Changing the oil early and choosing high-quality products can prevent many troubles. Regular maintenance is key to extending the transmission's lifespan and saving on repair costs. Safe driving comes first—when the light comes on, seek professional help to resolve it.