Be a meter reader

ECM data can be retrieved and graphed through a computer, though it requires the right software to translate the codes.

This is excerpted from the Overdrive 2008 Partners in Business manual for owner-operators. The next Partners in Business seminar will be held during the Mid-America Trucking Show in Louisville, Ky., March 19-21, 2009. To order a manual, call (800) 633-5953, Ext. 1301. Visit for more excerpts and information. The seminars and the manual are brought to you by Overdrive, ATBS and Castrol.

How much time did your truck idle last month? What percentage of your most recent trip did you spend in cruise? What was your average speed? How much time did you spend in top gear?
You may not know the answers to these questions, but they’re all readily available through your engine’s electronic control module. Data such as cruise speeds, gear engagement times, total idle time and numbers of hard stops can help you save fuel, limit engine wear and tear and improve safety.

Originally developed by Detroit Diesel as an integral part of the diesel injection system, ECMs quickly became standard equipment on all engines. Adding a vehicle speed sensor enabled ECMs to provide cruise control with no throttle linkage; additional sensors and programming helped track driver performance.

While the exact form of data may vary, every engine maker’s ECM tracks virtually the same raw information, which typically includes road speed, use and speed setting of cruise control, accelerator pedal position, engine rpm and a good deal about fuel, including total consumption, fuel consumed during idle and number of idle hours.

Whether you use a dash display unit or a personal computer to access ECM data, you can use it in several ways to reduce costs. Apart from the mechanical diagnostic functions of the ECM, such as fault codes, there are operational applications that will pay immediate dividends:

LOWER CRUISE SPEEDS. Because wind resistance increases with speed, especially above 50 mph, reducing speed improves fuel economy significantly. An ECM data report that shows trip times and speeds can show whether you need to slow down to save fuel.

Using cruise control also saves fuel by keeping the vehicle from straying above the intended cruise speed. Looking at cruise engagement time on the ECM data may show that cruise isn’t used often enough to get the best fuel economy. Many engine ECMs even provide an incentive, such as more torque or a higher maximum speed, to encourage drivers to use cruise control. Increasing the torque available in top gear reduces downshifting, essentially a way to improve fuel economy while also rewarding the driver for saving fuel.

REDUCE IDLING. Even experienced owner-operators sometimes don’t have a good idea of how much they idle. If you’re among them, seeing the number of hours idled can be a shock. It might even convince you to buy an auxiliary power unit or in-cab heater. Reducing idling is about more than saving fuel. If you use oil analysis to determine when to change, you’ll notice in the results that a reduction in idling reduces unburnt fuel and soot, allowing you to significantly extend your oil changes. Plus, research shows engines that idle less last significantly longer.

SHIFT PROPERLY. Cruising in the right gear, and even accelerating with progressive shifting (early shifts in the lower gears), can save fuel by making the engine more efficient. But many drivers run in too low a gear to avoid downshifting on the next hill or because diesels run smoother at higher rpm. Seeing a graphic display of the time spent in each gear can help you correct improper shift points. Especially critical is leaving the truck in top gear when appropriate during long climbs, which improves engine efficiency. Some programs even record how much time the driver spends in the sweet spot, the ideal cruise rpm for a particular engine. ECM data might also enable you to use a 13- or 18-speed gearbox to gain fuel economy, a practice especially recommended for Caterpillar ACERT engines.

STOP HARD STOPS. Data on hard stops can save fuel and improve safety because it is a key indicator of following distance. For example, a driver who backs off the throttle when slower traffic is ahead recovers energy in the form of inertia and uses it to push the truck down the road. A hard stop, by contrast, just throws the energy away. A following distance of at least three seconds is a safety must for avoiding a rear-end collision at higher speeds.