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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.
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Code 115 (J1939 SPN 612 FMI 2) means the ECM has lost both engine speed signals, crankshaft and camshaft, or reads them as erratic. Without engine position it cannot time the injectors, so it does not fuel the engine. Check both sensors, their connectors and the harness first.
First find out whether it is a magnetic pickup (two wires) or a Hall-effect sensor (three wires: supply, signal, ground). Check a magnetic pickup's resistance and a Hall sensor's supply voltage against the values in your engine's service manual, inspect the tone wheel, and check the connector and harness for damage or moisture.
Send us the code or alarm and what the generator is doing, and one of our engineers will help you diagnose it.
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A fault code names a symptom, not a cause. Our engineers have written the diagnostic sequence they use on site for this class of fault — ranked causes, ordered steps with the reading expected at each one, and the point at which to stop and call someone.
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