Case TR340B Engine Derate with DEF Dosing Fault
Fault Codes & Symptoms
Engine derated, MIL on Related symptoms: - DEF system faults - Warning lights on dash cluster - Reduced engine power The machine is low on power and has a warning light on the dash for the emissions system. It happened suddenly.
Confirmed cause: Failed DEF Dosing Pump. The pump motor was functional but an internal failure prevented it from building pressure correctly. Repair performed: Replaced the complete DEF pump/dosing module assembly. Primed the DEF system using the service tool. Verification: Ran the DEF Doser Pump Override test with the service tool. DEF pressure built quickly and stabilized within the manufacturer's specified range. Cleared all fault codes and operated the machine under load for an extended period. No fault codes returned and the engine derate was no longer active. Technician notes: - This fault presented like a pressure sensor issue due to the erratic readings. Testing motor resistance and verifying power/ground were key steps to rule out simpler electrical issues before condemning the expensive pump assembly. - The internal pump failure was not visible externally. The pump must be replaced as a sealed unit.