Does Your Preventive Maintenance Plan Actually Prevent Breakdowns?

Does Your Preventive Maintenance Plan Actually Prevent Breakdowns?

Preventive maintenance is more than a calendar event—it’s the secret sauce to fleet uptime, longevity, and reliability. But here’s the million-dollar question: Is your preventive maintenance plan actually preventing breakdowns, or is it just a glorified oil change schedule? 

In theory, a solid PM strategy should reduce costly repairs, extend component life, and keep CSA scores in check. In reality, many fleets follow outdated or incomplete schedules that merely delay the inevitable. 

If you’re still dealing with unexpected downtime, recurring component failures, or frustrated drivers, it might be time to overhaul your plan.

The Goals of Preventive Maintenance—And Why Most Plans Miss the Mark

A preventive maintenance program should be proactive, not reactive. The core goal is to catch minor issues before they morph into major breakdowns. That includes wear-related failures, fluid degradation, leaks, and even software glitches. But too often, shops treat PMs as a quick service interval—lube, oil, filter, next truck. That’s not preventive; that’s passive. 

Effective PM plans are built on data, standardization, and accountability. Every truck is different, and what works for a light-duty utility vehicle doesn’t cut it for a Class 8 heavy hauler. At S&D Auto & Truck, we’ve seen what happens when PMs are rushed or incomplete: trucks break down anyway, costing fleets both money and credibility.

What Your PM Plan Should Include

Most shops cover the basics: oil changes, fluid top-offs, brake checks, and tire pressure. That’s the bare minimum. A true preventive maintenance schedule goes much deeper. It includes:

• Torque and re-torque checks on critical fasteners like suspension bolts and hub assemblies
• Full driveline and U-joint inspection and lubrication
• Battery voltage/load testing and terminal cleaning
• ECM diagnostic scanning for fault codes and regen tracking
• Full HVAC system test for blower motor, compressor, and cab comfort sensors
• Electrical harness checks including ground wires and relays
• DEF system pressure testing and sensor validation

If your PM sheets don’t include these tasks—or if your techs skip them due to time constraints—then you’re missing critical opportunities to prevent mid-route failures. This is especially true for emissions systems. 

Today’s trucks are data-driven machines, and things like NOx sensor drift or faulty regen cycles won’t show up in a visual inspection. But they will show up on an ECM scan—assuming you’re doing one.

Signs Your PM Plan Isn’t Cutting It

Your preventive maintenance plan might be more reactive than you think. Issues often indicate that PM intervals are too long, inspections are rushed, or certain systems (like electrical or emissions) are being overlooked. Red flags include:

• Frequent roadside assistance calls and driver complaints
• Repeat repairs on the same component or truck
• Excessive aftertreatment issues (DPF clogs, forced regens, DEF failures)
• Tire wear that doesn’t match axle alignment or mileage
• Battery and HVAC system failures, especially in seasonal transitions

Another telltale sign? Drivers reporting issues that should have been caught during routine service. If your drivers are your diagnostic tool, your plan isn’t working. A strong PM plan should be one step ahead—not playing catch-up.

How to Use Data to Refine Your Maintenance Strategy

Want to stop breakdowns before they happen? Start tracking why breakdowns are happening in the first place. Every time a truck enters the shop for an unscheduled repair, log the failure mode and component. Over time, you’ll start to see trends—recurring air dryer failures, premature brake wear, or leaking coolant fittings. This data can reshape your PM approach.

Key metrics worth tracking:

• Most frequent component failures by mileage or operating hours
• Average time between failures for specific systems (brakes, HVAC, aftertreatment)
• Fault codes that appear consistently across different vehicles
• Downtime costs per vehicle per month
• Missed PM intervals and reasons why

Data helps you identify supplier issues, weak points in your program, and service gaps. Some fleets use telematics platforms to automate data collection and error code logging. Others rely on shop software and technician input. 

However you do it, the goal is the same: gather data, analyze trends, and adjust your fleet maintenance program accordingly. This transforms PMs from static intervals into dynamic, evolving systems that actually work.

Tech Training and Accountability Are Non-Negotiable

Even the best plan falls apart without execution. That means your techs must be trained—not just on general service procedures, but on your specific PM protocol. Torque specs, fluid analysis, diagnostic tool use, and even inspection technique all vary by vehicle type. Make sure your team knows what to look for. 

Accountability is just as critical. If PMs are rushed or pencil-whipped, then breakdowns are baked into your schedule whether you like it or not. You can implement random quality control checks or audit completed PMs. 

Take oil samples and verify that grease points were serviced. The message should be clear: PMs are not just about checking boxes; they’re about protecting assets. 

Turn Preventive Plans Into Real Protection

Preventive maintenance should do exactly what it says—prevent. If you’re still losing trucks to roadside failures, blowing budgets on emergency parts, or dealing with repeat repairs, it’s time to take a hard look at your PM strategy. 

At S&D Auto & Truck in Cumberland, RI, we help fleets evolve from reactive to proactive by implementing smart, data-driven maintenance programs that actually work. Stop settling for breakdowns as a “cost of doing business.” Build a plan that stops problems before they start. For more information, read our article on essentials for truck preventive maintenance.