What does it mean when the DEF light is on in JMC Transit?

[VanHayden]

JMC Transit DEF light on indicates a lack of water in the auxiliary water tank. Here are the extended details: 1. Auxiliary Water Tank: The auxiliary water tank is located under the driver's seat. Remove the seat cushion and the square iron plate to see the rectangular plastic box inside. If the vehicle has a power steering system, there is also a round plastic bucket nearby containing hydraulic oil. If the auxiliary water tank is short of water, it needs to be refilled immediately to resolve the issue. The reasons for the warning light include engine overheating alarm, damaged water temperature sensor, or lack of antifreeze. 2. Main Function of the Car Auxiliary Water Tank: When the car engine temperature is high, the liquid expands, and some antifreeze flows into the auxiliary tank through the tank cap. When the temperature drops and the cooling system pressure becomes negative, the system draws the antifreeze from the auxiliary tank back into the cooling system through the tank cap. The auxiliary tank also has corresponding markings to indicate the liquid level.