What causes the DEF warning light to illuminate in JMC Shunda?
2 Answers
JMC Shunda DEF warning light illumination may be caused by: engine overheating alarm; damaged water temperature sensor; or insufficient antifreeze. The DEF warning light in JMC vehicles indicates the auxiliary water tank warning light. When this light illuminates, it means the auxiliary water tank is low on water and requires immediate refilling to resolve the issue. Below are additional details: 1. Auxiliary water tank location: The auxiliary water tank is located beneath the driver's seat. Remove the seat cushion and the square metal plate to reveal a rectangular plastic container. For vehicles equipped with power steering, there's also a round plastic reservoir containing hydraulic fluid nearby. 2. Auxiliary water tank function: The primary purpose of the automotive auxiliary water tank is to accommodate expanding coolant when engine temperature rises, with excess antifreeze flowing into the auxiliary tank through the radiator cap. When temperatures drop and cooling system pressure becomes negative, the system draws antifreeze back from the auxiliary tank into the cooling system through the radiator cap. The auxiliary tank features marked levels indicating fluid quantity.
I've been driving a JMC Shunda truck for several years and have encountered the DEF warning light coming on several times. The most common reason is that the DEF urea level is too low, and the vehicle reminds you to refill it. Otherwise, the emission system may stop working, causing the engine power to be limited. Another common issue is a faulty sensor, such as a level sensor or temperature sensor malfunction, which can trigger a false warning light. It could also be due to a clogged exhaust system or contaminated DEF, where using poor-quality urea causes problems with the nozzle or SCR system. If there's an electrical circuit or control module failure, it can also trigger this light. I always check the fluid level first. If the light doesn't go off after refilling, I immediately head to a repair shop to scan for fault codes with a computer to avoid getting stuck on the road. The DEF system is related to emission regulations, and regular maintenance can save you a lot of money.
