DDEC III and DDEC IV ECM bench testing

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.

Most DDEC repair jobs will involve at least one ECM bench test and a circuit board inspection before a repair is started. The ECM bench test will test DDEC functions and if you provide a description of the symptom you observed and conditions which it occurs then the bench test will try to replicate that symptom.  If an ECM function fails to work, the symptom you reported or other abnormality is observed during bench test then the repair job moves on from testing to the circuit board inspection and then on to the repair. If all ECM functions work, the symptom you reported along with no other abnormalities are observed during the initial bench test then the repair job then you have three options.

The first option is to pay the cost of the first test and the return shipping and then we’ll mail your DDEC back. If the diagnostic tests you did on the truck were not very through and/or you found a broken wire, sensor, or switch that is likely the cause of the symptom you experienced then this might be the best option.The second option is to elect to open up the DDEC case and have a microscope aided circuit board inspection done. This is best if you are confident that you have done thorough diagnostics on the truck and engine side.The third option is to elect to run a more specialized test or additional testing time. This is best if the symptom you observed is not easily repeatable and only happens a few times a day and you are confident that you have done thorough diagnostics on the truck and engine side.As of 2021 I still offer DDEC repairs and testing to the general public. I have done jobs for OEM side engineers from some big names in the industry to do it yourself guys who have no diagnostic training and don’t even own a scan tool.I do not and will not have physical access to the engine and OEM side (truck) so whomever is pulling and reinstalling the ecm becomes the technician responsible for checking everything over and identifying the ecm as the cause of the problem. If you don’t have much if any experience diagnosing problems on Detroit’s and want to save a few bucks by not hiring a technician then it can end up costing you in the long run.Without physical access to the engine I won’t have access to enough information to tell you what the problem is unless I observe a problem with the DDEC. If your DDEC was fully functional and didn’t do anything abnormal during the bench test then I’ll tell you you’re DDEC was fully functional and during the duration of the test no abnormalities were observed or recorded. Some people ask…everything is ok then? I say…everything was ok during the test…outside of that I have no idea what problems your engine or truck might have or if an abnormality in the DDEC would have been observed ring an extended the testing period.


Extended tests can improve the chances of catching a symptom that only occurs once a day.

Testing can identify memory issues as well as well as other functions that fail to work such as Jakes and injectors.

DDECs like this can be fully functional and test fine despite being covered in oil. This is why an inspection is often a good idea after a test.

Estimated Cost

$100 and up + return shipping

  • a single overnight test is included in the price of most repairs and memory replacement jobs.
  •  a basic test is done on ecm check in and are included with most services
  • It’s worth checking for truck and engine side problems before getting into extended testing and it’s associated costs


Bench testing provides tests of ECM functionality during the testing it does not provide any information on ECM condition or expected remaining component life. This is where a physical inspection of the circuit board and its components can help. Also with the service plate removed more advanced (and expensive) ecm tests such as thermal imaging tests can be done.


Oil trapped underneath a layer of laminate

The formation of oxidation can indicate a water intrusion problem.

If necessary thermal imaging testing becomes an option after an internal inspection is done.

Estimated Cost

$300 + return shipping

  • The inspection cost are only due if no repair work is done otherwise, they are included in the cost of the repair.
  • Specialized tests or extended duration tests can add to the cost
  • Warranty claims that pass bench functionality tests can be subject to an inspection charge if an inspection is requested, and no ECM damage is found.