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Tips and advice on the Cummins Celect and Celect Plus engine platform:

  • Never pressure wash the ECM. The ECM is designed to handle road spray (even that fails eventually), but pressure washing will drive water and chemicals past the seals. This WILL destroy ECMs, and my void your warranty.
  • Fix oil leaks. Oil leaking down the harness like a wick and into the ECM can and does cause issues.
  • Always disconnect the ECM before welding. It is best to take off the C plug (injector harness) from the ECM before welding. If it is not possible or practical to remove C plug, at minimum disconnect the batteries completely and make sure the power wires to the ECM do NOT touch metal.
  • Always disconnect the ECM before changing batteries, working on the starter, alternator, or charging the batteries. Always remove the negative cable FIRST. Very much the same as the note above, ECMs don't like shorts or spikes in the power or on the ground plane (truck chassis). 
  • Never install battery cables backwards. Obviously you won't do this on purpose, but keep special attention when you connect the battery cables. Backwards cables happen more than you think, and the ECM is damaged instantly. 
  • Charge batteries, avoid jump starting. If your batteries are dead, it is ideal to disconnect the ECM from the batteries, charge them with your charger, then reconnect the ECM and start the truck normally.
  • Avoid mixing Celect and Celect Plus components. You can easily create a "Frankenstein" engine. This commonly happens when an engine is replaced with a different generation used engine. If you have to either upgrade a truck to Celect Plus, or put a Celect engine in a Celect Plus truck, you should do the full conversion. Electronics (including the ECM) should match the generation of engine you are using. The injector harness and OEM harness can be modified with a soldering iron or Dremel for the safety detents to fit, but you need the engine sensor harness to match the ECM. Please call us with questions you may have with this conversion. If you acquire such a mix of parts in  a truck, be sure to get a printout of your ECMs features and parameters. There are no conversion calibrations for using a Celect ECM on a Celect Plus truck (or vise versa), so knowing what was in the ECM will help tremendously in the event you need an ECM.
  • Inline fuses for the ECM power supply are common sources of issues. Also the ECM power supply wires tend to rub and short to the battery box.
  • Starting fluid only has 1 purpose on an electronic engine: Help start it. Specifically on a very cold engine that was not plugged in, and when the ECM does not have enough power to fire the engine during cranking due to excessive starter draw current.  A Celect or Celect Plus truck that is in good working order should never need starting fluid unless it wasn't plugged in during extremely cold weather. Starting fluid has little diagnostic value.
  • Keeping some basic supplies in your truck can help you diagnose issues on the road. Some items to keep in your truck include:
    • Cummins wiring diagram appropriate for your engine. Available from Cummins, they are amazingly affordable (considering they come from Cummins). The diagram will also have all the trouble codes and brief description of the code and other voltage, resistance, and misc technical specs.
    • Decent quality digital multi-meter. Auto-ranging is preferable, but not required. Make sure you keep an eye on the batteries, it is worth having a lithium battery for your multi-meter and check that it still functions yearly, at minimum. If you aren't familiar with using a digital multi-meter, check out youtube for instructional videos.
    • Pin-out adapters. Cummins (and others) make small bits of wire for checking your wiring with your multi-meter. The standard multi-meter probes are too big, so something smaller must be used. If you don't want to spend the money on the "proper" kit, large smooth paperclips work (be sure to smooth the end out to avoid scratching the gold off your wires).
    • Noid light to see if your injectors are getting power. Injector resistance is .5 to 1.5 ohms, or 1 ohm nominal.
    • Wire cutter/stripper/crimper, assorted connectors, electrical tape, extra spool of wire (12 gauge would be fine for most uses. Make sure it is copper conductor, multi-strand automotive type), alligator clips for making jumper wires, spare fuse holders and assortment of appropriate fuses.
    • Extra cam sensor (engine position sensor) and a tool to change it. The cam sensor is the 1 sensor that is necessary for the engine to run. If it fails, the engine cannot run.
    • Our phone number! That's right, we are here for free technical advice!


Fault Code 111

Fault Code 343

No start, no engine lights cycling

Possible Causes

  • Internal ECM problems
  • Voltage spike
  • Electrical Noise

  • Internal ECM problems​
  • Loose engine or chassis ground connections
  • Moisture in ECM connectors
  • Defective Alternator
  • Intermittent shorts to ground in these circuits can cause Fault Code 343: Injector solenoids, injector harnesses, fan clutch solenoids, fan clutch wiring, engine brake solenoids, engine brake wiring, OEM-installed engine speed sensors, flywheel housing and associated wiring, datalink wiring, and fuel shutoff solenoid or wiring.

  • No power to ECM from battery
  • Bad ground connection
  • No power from vehicle keyswitch
  • ECM damage
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  • Remove belt from alternator and run engine to see if the issue stops. If so, alternator is shorting to ground.
  • Clean battery terminals and grounding post.
  • If more than 3 counts and active, or engine will not run while active, ECM is faulty.

  • To determine if conducted electrical noise through the grounds is causing Fault Code 343, unbolt the ECM, and move it away from the engine block so that it is isolated from the engine block ground. If the fault is not duplicated, troubleshoot for the source of the electrical noise.
  • Clean ECM connectors with electrical connector cleaner.
  • Remove belt from alternator and run engine to see if the issue stops.
  • At this point, the ECM should be tested.

  • Check for power into the ECM at pins 20, 21, 22, 23 of the injector harness.
  • Check for ground at pins 9, 25, 27 of the injector harness.
  • Check for battery voltage at pin 26 WITH THE KEY SWITCH ON of the injector harness.
  • If you have power above and still dealing with a no-start, at this point the ECM should be tested.


We are still re-building this page. Please check back later or feel free to contact us for technical assistance.



DSO Industrial, LLC advises that all repairs should be done by certified heavy truck and equipment mechanics. Diagnostics and repairs of heavy equipment is inherently dangerous. Failure to follow this warning could result in property damage, injury or death. Under no circumstances shall DSO Industrial, LLC or any of its personnel be liable for any actions taken by anybody utilizing our online self help articles or person to person assistance.

On this page you will find some common technical issues, tips, tricks, other advice and some diagnostics you can perform. This page is focusing on Celect and Celect Plus issues only. We apologize for this page being quite dry and boring, but its hard to make technical articles exciting!

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