2 0 Caterpillar 3126 Engine Control Module (ECM) $550 USD Good used, cleaned, tested and inspected CAT 3126 ECM. Part Number: 239-3879. 30 Day Guarantee for swap or refund if not programmable. ECM's need to be programmed for your application. ConditionUsedFits To Make(s)CATERPILLARFits To Model(s)3126Part Number239-3879Stock NumberRyd 239-3879 MLS Number11387156CategoryEngine Control Modules (ECM) Last Updated12/18/2025 LocationFitchburg, MA, US Sold ByRydemore Heavy Duty Truck Parts (888) 519-___ SHOWNUMBERCall Seller Email Seller Save More Info