What does it mean when the JAC EPC light is on?

[McAthena]

When the JAC EPC light is on, it indicates that the system has detected a fault in the engine or electronic system. The reasons for the EPC light being on and the corresponding solutions are as follows: 1. First, check for faults in the intake system, such as leaks or blockages. 2. If the throttle body is dirty or has excessive carbon buildup, clean the carbon deposits in areas like the throttle body. 3. If the fuel used does not meet the required standards, promptly replace it with oil that meets the specifications. 4. If there is abnormal cylinder pressure or poor operating conditions, visit a 4S shop immediately for inspection and repair. 5. Rewrite the ECU-related data.

[OEmery]

The illuminated EPC light on JAC vehicles usually indicates electronic system issues. I remember encountering this recently while driving a friend's JAC Heyue - the dashboard suddenly flashed a yellow warning light mid-drive, making me think the engine was about to fail. Diagnostics later revealed the throttle body was as dirty as a range hood. The mechanic explained this system controls the accelerator, brakes and throttle body, with common culprits being faulty brake light switches, erratic throttle position sensors, or sticky throttle valves. It's particularly sensitive during cold winter starts - poor fuel quality or malfunctioning air flow sensors can trigger immediate computer warnings. While short slow trips might work temporarily, prolonged neglect can cause sudden power loss. Once I stubbornly drove 50km with the issue and got speed-limited to 40mph, nearly causing trouble. Nowadays, a 300-yuan throttle cleaning fixes it - much cheaper than tow truck fees.

[AshleyFitz]

My JAC Heyue's EPC light stays on, and I've been to the 4S store three times, gaining a lot of experience. The maintenance supervisor said that 90% of the owners face this issue due to carbon buildup in the throttle body. Last time, the mechanic showed me with an endoscope, and the back of the valve was as black as a coal mine. For a temporary fix, you can try turning off and restarting the engine—sometimes it can trick the computer. However, to really solve the problem, you need to check the fault codes, commonly P0121 for throttle signal abnormality or P2138 for mismatched throttle pedal signals. Also, don’t overlook the brake switch; last time, a Refine had its EPC triggered by a constantly lit brake light, and replacing the switch only cost a few dozen yuan. The most dreaded issue during repairs is wiring harness aging—the mechanic spent half an hour checking resistance values with a multimeter before finding the breakpoint.

[AbigailAnn]

The Jianghuai system illuminates the EPC light as the vehicle computer's self-rescue mechanism. When the engine receives conflicting signals, it actively triggers the yellow warning light—for instance, if the throttle fails to respond when accelerating, or when brake and accelerator signals conflict. Common triggers include air intake system leaks, where the mass airflow sensor misjudges the air intake volume. I've personally witnessed mechanics using smoke testers to identify cracks in intake pipes, with epoxy resin repairs successfully clearing fault codes. Additionally, unstable fuel pressure can cause issues, especially in vehicles converted to natural gas, where fuel rail pressure sensors frequently report errors. For prevention, focus on two key practices: clean the throttle body every 20,000 kilometers and consistently refuel at reputable gas stations, as inferior gasoline's gum deposits readily clog sensors.