Sprinter Electrical Systems

If you don't understand CAN, you CAN't get the job done


With most domestic vans and light trucks, the level of connectivity and complication is minimal compared to a Sprinter. The key to proper service and repair of this vehicle is the CAN - the Controller Area Network. Also called the CAN-Bus, it is a vehicle standard designed to allow all control units to communicate with each other and share data over a simple wired network.

The Sprinter is 100 percent Mercedes-Benz, not a Dodge/Freightliner chassis with a Mercedes engine. As such, the Sprinter is not an a la carte vehicle that has components picked from multiple suppliers like many domestic trucks. It has all Mercedes components, designed to work together at the factory.

Consequently, the Sprinter does not diagnose like Dodge, Isuzu or Ford vehicles. Mercedes vehicles log a lot of fault codes and event codes for most operational faults. Being able to read and understand fault codes on all control units is vital to diagnose CAN-Bus problems.

To better understand the fundamentals of the Sprinter's electrical system, Fleet Maintenance Magazine editor David A. Kolman visited with Eric J. Ord, a highly regarded independent source of Sprinter technical information. Ord has developed three separate scan tools for the Sprinter, one of which was delivered to all the locations in the U.S. and Canada for the world's largest fleet operator. Over the years, Ord has conducted more than 100 training courses on the Sprinter and has written numerous technical materials on Sprinter diagnosis and repair.

Ord is managing director of Megara LLC. With offices in the U.S. and Europe, the company is involved in projects with several commercial and municipal fleets on Sprinter vehicles, as well as other projects for U.S. and foreign military customers with Mercedes-Benz vehicles.

NUMEROUS CONTROLS

For most domestic vans and light duty trucks, the CAN-Bus traditionally has limited application, usually with the few sensor values shared between the engine, transmission and instrument cluster, Ord explains. With Sprinter, there are a lot of control units and sensors that, share information and transmit signals.

On the average model year 2002 to 2006 Sprinters, there are generally around 11 or more individual control units on one CAN-Bus network, he says. For 2007 to 2010 models, there can be more than 29 control units on three networks.

"Without a CAN-Bus network, a Sprinter would have either miles of wire or many duplicate sensors or both," he says. "The cost of all of this copper would add thousands of dollars to the vehicle price and hundreds of pounds of weight.

"The Sprinter is a Mercedes and Mercedes parts tend to be expensive. If the approach to solving a problem is just to replace parts until the problem goes away, that will put you upside down on the vehicle quickly."

CAN BEGINNINGS

The vehicle CAN-Bus concept was pioneered in Germany by Robert Bosch GmbH in the 1980s. Daimler-Benz AG was one of the first to adopt CAN-Bus for vehicles. In 1991, Mercedes-Benz started using a CAN-Bus for communications between electronic control modules (ECM) in passenger cars on the W140 S-Class 600SEL.

For commercial vehicles, the CAN-Bus has been implemented since the 1990s in two forms: a two-wire CAN for vans and light commercial vehicles, and a four-wire CAN for trucks and heavy equipment. The difference between the two CANs is double redundancy of signals versus single redundancy. Both systems use a twisted pair cabling to minimize interference.

When Mercedes designed the Sprinter back in the 1990s, Ord says the company saw the need to have all of the control units and sensor values shared over an automotive/industrial standard Bus system. The earliest European Sprinters had a very simple CAN with very few components linked. For North American Sprinter models, starting in 2002, CAN-Bus is used for all main systems and controls for powertrain, interior, chassis, etc.

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