DDEC ECM testing and inspections
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Not sure if a DDEC III or DDEC IV is the cause of a problem you’ve been trying to find?
In addition to stereoscope assisted ECM circuit board inspections and the standard ecm bench testing DCS also offers a variety of more specialized ECM bench tests ranging from the external data monitoring of an engine input such as oil temperature to thermal imaging of a DDEC during cold start up. We can even link multiple DDECs together to test the big 16 cylinder Detroits.

DDEC IV programming
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The DDEC IV control system is used on everything from 2 stroke marine applications to highway applications.

DDEC III programming
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The DDEC III control system is used on everything from 2 stroke marine applications to highway applications. No J1939, Elog, or EGR engine functions available. Not suitable for gliders

DDEC III and DDEC IV circuit board repairs and damaged component replacement
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Many of the major components inside a DDEC III or DDEC IV had an expected service life of 50 years or more. Premature failures are not uncommon but most of the time when something like the primary microprocessor or the analog to digital converter fails it’s because the component suffered damage from heat, too much current, oxidation damage from water or battery acid, or exposure to voltage that exceeded the components maximum rated voltage. Sometimes the damage is immediately obvious and sometimes it isn’t and requires component specific tests to be identify and locate as it did with the 9308 DDEC IV in this photo

DDEC III and DDEC IV Case, service plate, and connector replacement
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I don’t have a problem with making repairs to ECM with lots of case damage and proving warranty for that repair as long as the case is keeping the water out, has at least 3 mounting ears, supports the oem and engine side connectors on the sides and, isn’t cracked. Otherwise I’d need the broken case replaced to be able to provide warranty on the repair I made inside.

DDEC III and DDEC IV memory and battery replacement
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When it comes to DDEC ecms with internal batteries (DDEC IV and up) The most common ecm component failure is the internal battery buy a mile followed by memory. Some DDEC IV software versions will trigger an active flash code 46 (SID 214): “RTC backup battery low” when the internal battery voltage drops below 2 volts. Flash code 53 Nonvolatile memory failure and/or Nonvolatile memory data incorrect (Flash 53) is triggered from an invalid checksum that’s purpose is to detect data corruption in a DDECs program. Both Flash 46 and 53 cannot be cleared while active.

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The engine control module (ECM) is without a doubt the most widely misunderstood component on a modern engine. The ECM is the only part of the engine that cannot be easily evaluated. It’s easy to feel if a cylinder liner has been scored. It’s easy to see if a camshaft lobe is flaking but if an ECM is responsible for a no start, misfire or poor fuel mileage or horsepower it’s not so easy to be sure the ECM is the problem. Speaking of misfires an electronic injector is another example of a component that can be difficult to diagnose. With an injector you can switch the suspected injector with a known good injector and see if the problem follows the injector. Sometimes this method identifies the bad injector and sometimes it doesn’t. Depends on what the problem is. Now let’s apply that logic to an attempt to determine if an ECM is bad. Let’s say a Freightliner glider has a no start condition. If you switch that ECM with another that’s off of a Freightliner glider you can be about 90 percent sure of any conclusions you reach. However if that Freightliner glider has an ignition relay and you swap the Freightliner’s DDEC IV with a known good DDEC IV from a Fitzgerald 389 the 389’s ECM will not start the Freightliner. The differences in programming between the two DDEC IV ECMs adds many variables to the test. Things gets even worse when trying to determine the cause of poor fuel mileage and horsepower. Let’s say the poor performing engine is a 1999 12.7 MK60 running a DDEC IV and the test DDEC IV was pulled from a 2001 12.7 MK60. Not only do those two engines run different cams but they have different compression ratios. The injector trim codes are almost never the same so unless they are programmed specifically for the test the wrong injector trims can throw off fueling by as much as 20 percent. There are hardware differences between DDECs as well but I’ll get into all that some other time. Unless $2000 for a reman DDEC is pocket change for you then it’s worth the time to be mindful of all the variables when diagnosing a suspected ECM problem.




Shipping Address

(Ship ECMs that need service and ECM core returns here)

Diesel Control Service Suite #395

1151 Freeport Rd

Pittsburgh, Pa 15238



7 a.m. to 7 p.m. EST Mon-Fri





DCS ECM Lab Address

615 Pillow Ave.

Cheswick, Pa 15024


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