The 2021 Honda Passport's 3.5L V6 features Variable Cylinder Management (VCM), which deactivates cylinders during light-load driving to improve fuel economy. While VCM technology has improved over the years, some owners experience issues or simply dislike how it operates. Here's what you need to know.
How VCM Works in the Passport
VCM can deactivate up to three cylinders when the engine doesn't need full power. During highway cruising, gentle acceleration, or light-load conditions, the system runs on three or four cylinders instead of all six. This improves fuel economy by reducing pumping losses and friction.
The system uses solenoid-actuated rocker arms that can lock out, preventing the valves from opening on deactivated cylinders. The engine computer manages cylinder deactivation seamlessly, though some drivers notice a subtle change in engine feel during transitions.
Common VCM Concerns
Oil consumption is the most frequently cited VCM concern. The theory is that frequent cylinder deactivation/reactivation causes increased piston ring wear, leading to oil consumption. Some owners report consuming a quart every 3,000-4,000 miles, which Honda often considers within "normal" range.
Vibration during VCM operation bothers some owners. When running on fewer cylinders, the engine's balance changes, and some perceive this as roughness. Honda uses Active Noise Cancellation to mask VCM sounds, but vibration remains perceptible to sensitive drivers.
Spark plug fouling can occur on cylinders that deactivate frequently. Oil vapor from the crankcase can accumulate on spark plugs in deactivated cylinders. This is typically minor but can contribute to rough running over time.
VCM Disablers
Aftermarket devices that disable VCM are popular among Honda owners. These plug-in devices prevent VCM activation, keeping all cylinders firing at all times. Owners report smoother operation and reduced oil consumption, though fuel economy decreases slightly.
Popular options include the VCMuzzler, VCMtuner, and similar devices ranging from $50-150. These devices don't modify the ECU permanently and can be removed if needed for warranty service.
Warranty Considerations
Using a VCM disabler could potentially void warranty coverage for engine issues if Honda determines the device contributed to the problem. However, many owners use these devices without warranty issues. The Magnuson-Moss Warranty Act requires manufacturers to prove a modification caused a failure before denying coverage.