Generator shuts down; controller displays Fault Code 156 – Low Coolant Level

Safety first: Let the generator cool fully before opening the cooling system. Pressurized hot coolant can cause severe burns.

• Inspect coolant level: Check the level in the expansion tank and at the radiator (when cool). If low, top up with the correct premixed coolant recommended by Cummins.
• Check for leaks: Look for dried coolant residue or wet spots around hose connections, radiator core, water pump weep hole, and engine block plugs. Tighten clamps and replace cracked hoses.
• Low coolant sensor: Locate the low coolant level switch or sensor in the radiator or expansion tank. Inspect wiring and connector. If the coolant level is correct but the fault persists, the sensor may be stuck or failed and should be replaced.
• Radiator cap: Inspect the radiator cap seal and spring. A weak cap can allow coolant loss. Replace with the correct pressure-rated cap for your Cummins model.
• Reset: After topping off and fixing leaks, clear the fault on the controller and run the unit while monitoring for further coolant loss.