Generator Fault Code Database

ECM Critical Internal Failure (J1939 SPN 629 FMI 12)

Cummins fault code 111 is reported over J1939 as SPN 629 FMI 12: the Electronic Control Module (ECM) has detected a critical internal failure (bad intelligent device or component). It points to the ECM itself, typically its internal memory or internal voltage supply, rather than an engine sensor, and the engine may not start. Note: J1939 SPN 111 on its own means coolant level, which is a different fault.

Engine Speed/Position Signals Lost (J1939 SPN 612 FMI 2)

Cummins fault code 115 is reported over J1939 as SPN 612 FMI 2: the ECM has lost both engine speed/position signals, the primary (crankshaft) sensor and the backup (camshaft) sensor, or reads them as erratic or reversed. Without a valid speed signal the ECM cannot time fuel injection, so it stops fuelling: the engine cranks but will not start, or shuts down while running.

Engine Speed — Overspeed, Underspeed and Sensor Faults

SPN 190 is the engine-speed signal; the FMI says whether the engine is over speed, under speed or the sensor is at fault. Overspeed first: the engine has exceeded its maximum safe operating speed. This protection fault activates when engine RPM surpasses the manufacturer's specified limit, typically 10-15% above rated speed. Engine overspeed can cause catastrophic mechanical damage including connecting rod failure, piston damage, and crankshaft breakage.

Engine Oil Pressure — Low, High and Sensor Faults

SPN 100 is the oil-pressure signal; the FMI beside it says whether the reading is low, high or a sensor fault. This page covers LOW pressure (FMI 1, 17, 18): oil pressure has dropped below the minimum safe operating threshold. Low oil pressure can cause severe engine damage within minutes as bearings, pistons, and camshafts rely on pressurized oil for lubrication and cooling. This fault requires immediate engine shutdown to prevent catastrophic failure.

Fuel Pressure Low

The fuel system pressure is below the minimum required for proper injection. Low fuel pressure prevents adequate fuel delivery to the injectors, causing hard starting, loss of power, rough running, and potential engine stalling under load. Modern common-rail systems require precise fuel pressure for proper atomization.

Intake Manifold (Boost) Pressure — High, Low and Sensor Faults

SPN 102 is the boost-pressure signal; the FMI says whether boost is high, low or the sensor is faulty. This page covers HIGH boost (FMI 0, 15, 16): the turbocharger is producing excessive boost pressure beyond normal operating parameters. Over-boost raises peak cylinder pressure and can lead to head gasket failure and engine damage. Common causes are a wastegate or VGT actuator stuck closed or a faulty boost sensor. (Black smoke usually points the other way: too little boost.)

Intake Manifold Temperature High

Air entering the engine from the turbocharger is excessively hot. High intake air temperature reduces engine power, raises exhaust temperature and makes the ECU derate the engine. This fault typically indicates a problem with the charge air cooler (intercooler) or ambient temperature issues.

Engine Coolant Temperature High

Engine coolant temperature has exceeded the maximum safe operating limit. Overheating can cause severe engine damage including head gasket failure, piston scoring, and potential engine seizure. This is a shutdown-class fault that requires immediate attention.

Fuel Injector Rail Pressure Low

The high-pressure fuel rail in the common-rail injection system is not achieving required pressure. Modern diesel engines require very high fuel pressure (1,600-2,000+ bar) for proper atomization. Low rail pressure causes poor combustion, white smoke, hard starting, and significant power loss.

Engine Start Fail

The DSE controller has attempted to start the engine but the engine has not reached the preset running speed within the configured start time. This fault will stop the starter motor and prevent further start attempts until the fault is acknowledged and cleared.

Underspeed Warning

Engine speed has dropped below the minimum threshold configured in the DSE controller. This typically indicates the engine is being overloaded or is experiencing fuel delivery problems. If not corrected, it will progress to an underspeed shutdown.

Low Oil Pressure Shutdown

Engine oil pressure has dropped below the shutdown threshold and the DSE controller has stopped the engine to prevent damage. This is a critical protection fault. Do not attempt to restart until the oil pressure issue is diagnosed and resolved.

Low Fuel Level Warning

The fuel tank level has dropped below the warning threshold configured in the DSE controller. This is a warning-class fault alerting operators that refueling is required soon. Continued operation without refueling will result in engine shutdown.

High Coolant Temperature Shutdown

Engine coolant temperature has exceeded the maximum safe limit and the DSE controller has shut down the engine to prevent thermal damage. This fault will lock out the controller until acknowledged. Do not restart until the cooling system is diagnosed.

Emergency Stop Active

An emergency stop button has been pressed or the emergency stop input is active. The DSE controller has immediately shut down the engine and will not allow restart until the emergency stop is reset and the fault cleared.

Generator Over Voltage

The generator output voltage has exceeded the maximum safe limit. Over voltage can damage connected equipment and indicates a problem with the Automatic Voltage Regulator (AVR), generator excitation, or voltage sensing circuits.

Generator Under Voltage

The generator output voltage has dropped below the minimum acceptable level. Under voltage can cause connected equipment to malfunction and indicates problems with AVR, excitation, speed control, or overloading.

Low Oil Pressure Warning

The ComAp controller has detected engine oil pressure below the warning threshold. This is an early warning before shutdown level is reached. Immediate attention is required to prevent engine damage.

Engine Overspeed Shutdown

The engine has exceeded maximum speed and the ComAp controller has initiated an emergency shutdown. Overspeed protection prevents catastrophic engine damage from mechanical failure due to excessive rotational forces.

High Coolant Temperature Shutdown

Engine coolant temperature has reached the shutdown threshold. The ComAp controller has stopped the engine to prevent heat damage. Do not restart until the cooling system has been inspected and the cause determined.

Fail to Start

The ComAp controller has attempted to start the engine the configured number of times but the engine has not reached running speed. Further start attempts are locked out until the fault is cleared.

Generator Over Frequency

The generator electrical frequency has exceeded the maximum threshold. Over frequency indicates engine speed is too high, which can damage sensitive electrical equipment and indicates a governor problem.

High Coolant Temperature

Engine coolant temperature has exceeded the safe operating limit. This protection fault triggers warning or shutdown depending on temperature level. Overheating can cause severe engine damage including head gasket failure and piston seizure.

Low Engine Oil Pressure

Engine oil pressure has dropped below minimum safe level. This critical fault triggers shutdown to prevent bearing damage and engine seizure. Do not restart until oil pressure issue is diagnosed and resolved.

Low Fuel Pressure

Fuel supply pressure to the injection system is below required specification. Low fuel pressure causes hard starting, power loss, rough running, and can lead to injector damage from inadequate lubrication.

Reverse Power/Motoring

The generator is absorbing power from the grid instead of supplying it. This dangerous condition occurs when engine power drops below the power required to overcome system losses, causing the generator to act as a motor.

Earth Fault Detected

An earth (ground) fault has been detected in the generator output circuit. Earth faults indicate dangerous leakage of current to ground, which can cause electrocution hazards, equipment damage, and fire risk.

J1939 Network Communication Error

The ECM has lost communication with other modules on the J1939 data network. This fault affects data exchange between ECM, transmission, instrument cluster, and other networked components.

Battery Voltage Low

The DC control battery voltage has dropped below the minimum operating threshold. Low battery voltage can prevent reliable engine starting and may cause controller malfunction.

Loss of Speed Signal

The ComAp controller has lost the engine speed signal during operation. This can cause engine shutdown as the controller cannot determine if the engine is running or at correct speed.

Engine Overspeed

The engine has exceeded the maximum safe operating speed limit. The ECM has initiated protective shutdown to prevent catastrophic mechanical failure from excessive rotational forces.