DDEC inputs and outputs: “Caution: To avoid personal injury, only replace with an ECM that has the identical inputs and outputs programmed”
DDEC III and IV ECMs each come with a bright yellow label with the above words written on it. This warning is frequently ignored by DDEC owners but this warning is for them and technicians that are new to the DDEC systems. You almost never see warnings like this on Caterpillar and Cummins ECMs and I’ll tell you why.
DDEC ECMs are among the most diverse and versatile ECMs in the ever made. With advanced programming techniques, the same box that runs a 1993 two stroke marine engine can be made to run a 2004 four-stroke EGR engine on a truck. You don’t see versatility like that in a Cummins or Caterpillar ECM. The downside? Lots and lots of software variations and options, even amongst truck models and years. The connectors are NOT keyed differently. Then the only thing stopping a Series 60 owner from plugging in a used 2-stroke marine DDEC into his wiring harness and turning the key is that yellow warning label. Situations like that don’t happen too often but input and output mix-ups among Series 60 truck DDECs happen all the time. Depending on what settings are wrong the DDEC might fail to engage or disengage the fan, the cruise, the jakes, the warning buzzer, the engine safety parameters, and in some cases not even start the engine or communicate. A typical mix-up is using a DDEC programmed for a Kenworth in a 99 International. When this mix-up happens the idle validation input connects to the manual fan input, so anytime the throttle is pushed the fan comes on.
This isn’t something that DDEC owners need to think about until they have an ECM failure. Once that happens there is a chance I can recover the DDEC data from the core DDEC or from any spare DDEC you know runs without problems. If not the dealer can download your original factory inputs and outputs from Detroit. A third option requires some preparation before you have a failure but is worth it.
Next time you have a technician plugged into your Series 60 ask them to make you a copy of your input and output settings. This way you won’t be forced to go back to Detroit or worse yet guess as to what your inputs and outputs are. If you’re good with electrical you can figure this out for yourself but it requires some time studying your wiring harness. Just be aware there are 25 programmable pins that need set and about 140 additional parameters that need defined every time a DDEC is configured for a specific truck.
Written by Fernando DeMoura, Diesel Control Service