“What Hath God Wrought?” That was the first telegraphic message that Samuel F. B. Morse dispatched on May 24, 1844, over an experimental line from Washington, D.C., to Baltimore. At either end of the line was a device used to transmit and receive an alphabet of electronic dashes and dots used to form telegraph messages – Morse Code.
Essentially, Sam Morse had invented the first bus network! But oh, how they’ve evolved.
Vehicle systems are highly integrated with one another, sharing data that each system needs over a communications line that connects them all. This sharing of data reduces clutter and cost but if something happens to impede that communication, a variety of problems could result. In the case of the example used in this month’s edition of The Trainer, the complaint is an ABS (Anti-lock Braking System) warning lamp that is illuminated on the dash. And as you know, if the lamp is illuminated, the system is offline until its repaired.
Several factors come into play when tackling a “U” code. What kind of network is it? Are there other networks on the vehicle? Is there a “gateway” module or do the networks connect directly to the DLC (Diagnostic Link Connector)? If there is a gateway module, does the OE security protocol allow me to connect directly to the various modules or just to the gateway?
But don’t let that hold you back. Taking on these DTCs is no different than other new systems you’ve learned. Follow a process, understand the system and why that particular code is set, and you’ll improve your chances of nailing down the cause on the first try.
