A P0300 random misfire code in your 2018 Ram 1500's 5.7L Hemi accompanied by suspected Multi-Displacement System (MDS) malfunction indicates the cylinder deactivation system may be causing combustion irregularities. MDS problems create misfire-like symptoms that trigger P0300 codes.
Understanding MDS Operation
The MDS system deactivates four cylinders during light load cruising to improve fuel economy. Special lifters on cylinders 1, 4, 6, and 7 can disable valve operation, while fuel injection to those cylinders is cut. The system activates and deactivates seamlessly when functioning correctly.
MDS Malfunction Symptoms
When MDS malfunctions, symptoms include rough running during cylinder deactivation, audible changes in engine sound when MDS engages, misfire codes during MDS operation, and a distinct ticking noise. Some owners describe a sensation similar to driving over rumble strips.
MDS Lifter Problems
The specialized MDS lifters can collapse or malfunction, causing ticking noise and misfires during deactivation. These lifters are different from standard hydraulic lifters and have a higher failure rate in some production runs.
MDS Solenoid Issues
Oil control solenoids manage MDS lifter operation. Solenoid failures, wiring issues, or oil supply problems prevent proper lifter control, causing rough MDS transitions or failure to deactivate cylinders properly.