Tips and pics


Is Your ECM Ok?

When you turn the ignition key on, the “Stop” and “Check” engine lights should come on, then cycle off after a couple of seconds.

If the lights don’t come on at all, check for 12V in the “C” Plug (Actuator harness. Top-inside plug) at pins 20, 21, 22, and 23 at all times and pin 26 with the key on. If you have power at all those pins, the ECM is bad. If you don’t have power, check the inline fuses to the right of the ECM. Also, check for a fuse in the battery box.

How Dead Is Your ECM?

There are a few different levels of non-functionality. When you turn the key to the ON position:

  • Stop Engine/Check Engine/Engine Warning Lights Come on and Go Back Off (Normal)
  • Stop Engine/Check Engine/Engine Warning Lights Come on, Go Off, and Come Back On (Active Fault)
  • Stop Engine/Check Engine/Engine Warning Lights Come on and Stay On (ECM Locked Up)
  • Stop Engine/Check Engine/Engine Warning Lights Don’t Come on at All (ECM Not Powering Up)
How Dead Is Your ECM

Oil in Your ECM

A leak at the valve cover where the injector wires pass through can let the oil run down the loom and find its way into the ECM through the actuator “C” connector. Because oil is conductive, covering a circuit board with oil causes multiple components, mostly programmable memory and processing chips, to short out and fail. Depending on the severity of the short, this may or may not render your ECM non-rebuildable. Should you find that you have a leak allowing oil to travel down the wire loom, it’s best to remedy the situation before it damages your ECM.

Oil-Soaked ECM

Oil Soaked Circuit Board with ChipsOpened Oiled ECM Circuit BoardAnother Oiled Electronic Circuit Board with Chip Components

Water-Damaged ECM

Most of us have done it; you know, dropped our phone in the toilet, creek, etc. How well did it work for you after that? Maybe some intermittent shorting going on? So, the same thing goes with ECMs. Electronics and water don’t mix.

Another Water Damage ECM Circuit BoardWater Damage ECM Circuit Board

Results from a Water-Damaged ECM

Burnt ECMs

Burnt ECM's
Burnt ECM's
Burnt ECM's

No Good

Plugs from the wiring harness tend to get corroded and stick in the ECM. If you wiggle and pry back and forth too much on the harness plug, the computer circuit board can crack, rendering the ECM no good and not rebuildable.

No Good
No Good
No Good

It's Doing the Same Thing

“Insanity is doing the same thing over and over again and expecting different results.”

Albert Einstein

It's Doing the Same Thing

Hopefully, when you buy a new part and install it, it fixes the problem, and it’s not doing the same thing. But, if it is doing the same thing, would you buy that same part again and put it on, thinking it would fix it this time? In most cases, one would think not. Most would search a different area and maybe even return the part that didn’t fix the problem.

This is somewhat of a common thing with rebuilding or replacing ECMs. Electronic Control Modules are the brain of the engine, controlling many different parts of the engine. So, depending on the codes, there are many different parts to test before finding the exact problem.

So, is your truck “doing the same thing” after you put a new ECM in it? Well, we hope not, but maybe that wasn’t the problem. Do some more digging and see if you have some bad wires or sensors causing your truck to run badly or not at all.

You could always have coffee with the crew and see if they have any suggestions, or give Midwest ECM Repair a call and see if they can help you diagnose the problem. Maybe even send it in to get tested for free.

A cooling plate is not needed for an ECM rebuild; it costs more for shipping, fuel, and mechanical costs. However, we have used Cummins ECM cooling plates for the purchase of $150.

Fuel Shutoff Solenoid

The fuel shutoff solenoid is one of the components that can take out an ECM. The ECM supplies +12V to the fuel shutoff solenoid through pin 16 on the actuator/injector harness (C-Plug) when it has +12V on pins 20, 21, 22, and 23, and also +12V on pin 26 from the ignition key. Not only does the ECM supply the +12V, but it also monitors it. If the coil inside the solenoid fails, it can short to ground via the housing. This, in turn, starts pulling down the +12V. The ECM will ramp up amperage in an attempt to maintain 12V on pin 16. The ECM will actually burn itself up attempting to push +12V.

It’s a good idea and cheap insurance to change your fuel shutoff solenoid when installing a new ECM.

Fuel Shutoff Solenoid
Fuel Shutoff Solenoid

Cummins Celect and Celect Plus Harness Connections

Celect and Celect Plus have different plugs, kind of like your home computer, so you can’t mess it up. Well, of course, it still happens. Both Cummins Celect and Cummins Celect Plus ECMs have three wiring harness connections with 28 pins each. Always check to make sure your plug is seated securely and making good contact (not too much lube). Too much grease or incorrect grease used to waterproof can cause connectivity problems. A light film of dielectric grease is all that’s necessary. Sometimes one of the 28 pins can get bent when plugging and unplugging the connectors for troubleshooting, causing connectivity problems. Inside each connector is 28 female ends. These become dirty, corroded, and stretched over time which makes for a poor electrical connection and can cause intermittent problems. Spraying electronic contact cleaner into the harness ends and blowing out the dirt can help maintain a proper connection.

Cummins Celect and Celect Plus Harness Connections

The 28 Pins and the Connectors

The A-plug or Sensor connector is the one on the bottom outboard from the block when the ECM is mounted on the engine. This connector houses engine position, coolant temperature, coolant level, ambient air temperature, ambient air pressure, manifold air temperature, boost pressure, oil temperature, and oil pressure, along with connections from control data links, service tool data links, and diagnostic signals.

The second one is the OEM connector or B-plug. This one is on the top, outboard from the block when mounted on the engine. This harness houses the vehicle speed data, tachometer, idle validation, and throttle position, along with all the cab switches—clutch, brake, cruise on/off, cruise set/resume, engine brake, and idle increment/decrement. This connector also provides the signal to the stop engine, check engine, and engine protection lamps.

The third is the Actuator connector or C-plug, often called the injector harness. This one is on the top inboard toward the block when mounted on the engine. This connector houses the four un-switched +12V lines, the key switch +12V line, three battery returns or grounds, the power wires for the fuel solenoid, engine brakes, and the fan clutch. This connector also has supply and return lines for all six injectors.

Did a Hurricane Get Your Truck?

Saltwater destroys electronic components faster than anything else. We’ve had several ECMs come to us from the Eastern Seaboard following superstorm Sandy. Here are some pictures of what’s happened to the ECMs. You can imagine if the inside of the ECM looks like this, there’s extensive corrosion damage to the wiring harness and sensors. Just replacing the ECM in these circumstances usually doesn’t completely fix the truck.

Water Damaged ECM's

Water Damaged ECM's

Remaned or Rebuilt vs. Repair

The difference between a remanufactured or a rebuilt ECM and a repaired ECM will help you understand what you are paying for, where to go, and where not to go.

The basic difference is a remanufactured ECM is totally remanufactured to the original build and exact specifications and is tested to original equipment standards. There is nothing short in it from a new ECM, but just the name it carries, remanufactured! In the case of repaired ECM, the repair is done up to the level of failure for which there was a need for fixing; apart from that, components are left intact. The remanufactured ECM is tested on a test station; better yet, some run it on a test truck.

So the quality aspect of a remanufactured ECM is superior. All the parts of the ECM are up to the original marks, and nothing is left to chance. In the case of a repaired ECM, only failed, worn-out, and corroded parts are replaced. It directly indicates that you are at more risk of getting frustrated due to repeated failures, which were left untouched at the time of repair.

You should know what you’re paying for. It is clear and obvious that the cost of a repaired ECM is far less as compared to the remanufactured or rebuilt ECM, but as is the price, so is the quality. There may be additional downtime and more servicing for a repaired ECM because the components are replaced as needed, and not all companies test the ECM on a test station or even a test truck.

Another advantage of remanufactured ECMs is that you get a warranty period from the company. So repaired ECMs may appear alluring, but in reality, remanufactured ECMs are more quality filled and, of course, valuable for your money.

It is clear that the situation depends upon your requirement and what money you can spend on your ECM and truck. How much longer will this truck be used?

Renamed or Rebuilt vs. Repair
Remaned or Rebuilt vs. Repair

Broken Piston Skirt

“If you turn it up, you’ll burn it up,” don’t believe it.

First off, all of the electronic engines have steel top pistons, and they can’t burn (you also cannot burn a hole through them). We have contacted several shop owners who we do business with on a daily basis and have asked them if they have ever seen a two-piece steel top piston burn, and the answer is always “No!” However, the piston skirt is aluminum, and it can break, and when that happens, the piston head, which is the steel portion that doesn’t burn, goes sideways or flops over and breaks the liner. This situation is not called “burning a piston.” It’s losing a piston skirt. Yes, serious damage has occurred, and now your engine needs a cylinder kit and a head, but your piston is not burned.

Lugging your engine is the main culprit of a broken piston skirt. The harmonics in an engine being lugged are far greater than in an engine that is allowed to run free. When running in the hills and mountains, use a lower gear and keep your engine at its “sweet spot” (such as 1500 or higher on the tach). You drive your truck every day, and you should know the sweet spot. Your turbo boost gauge, pyrometer, amount of throttle, and the feeling you get through your seat will help you to determine the sweet spot of your engine. Keep your engine at or near its sweet spot, and you’ll minimize the chances of lugging and breaking a piston skirt. By the way, it’s your engine, and you should be able to do with it as you please. After all, you are the one paying for it.

Back in the early 1990s, several low-horsepower engines were built with aluminum pistons. These aluminum pistons can get a hole burnt through them (actually, they crack, and then the flame from the burning of the fuel burns a hole through them). This does not happen to steel top pistons. In fact, a steel top piston is so strong that if a valve breaks off, the piston will beat the broken valve into the cast iron of the head, and there will be very few marks on the piston. Detroit Diesel was the first engine company to use a two-piece steel top piston. Today, all of the Detroit, Caterpillar, and Cummins pistons are made by the same company, Mahle, which is based out of Michigan. So we all have something to thank the Detroit Diesel engineers for the invention of the two-piece steel top piston.

All of the older mechanical Cummins and Caterpillar engines have aluminum pistons, and that is why they coat them with ceramic and Teflon. The ceramic on the top of the piston reflects heat and keeps it in the combustion chamber to better burn the fuel, and the Teflon on the skirt allows the piston to move more freely in the cylinder liner. You also can coat the newer steel top pistons and aluminum skirts with the same coating. It is a two-week process to coat the pistons.

So the next time a service manager or mechanic tells you you’re going to burn it down or burn a piston in your electronic engine if you turn it up, just ask him if he has ever seen a burned steel top piston. If he says yes, ask to see it (and then please send it to us because we would love to see it too). If he says yes, you pretty much know that he’s lying, so should you trust anything else he has to say?

Don’t forget, when dealing with high-performance products for your engine, trust your instincts and your gut feelings.

Broken Piston Skirt
Broken Piston Skirt