Some of your most serious car problems can also be the hardest to diagnose. That’s because they concern the one part of your car that you count on to help you diagnose issues.
Your car’s ECM, or Engine Control Module is frequently called your car’s brain. This computer system is also known as an ECU (Engine Control Unit). It controls parts of your car’s engine that have to do with driveability and performance.
Newer model cars have a PCM, or Powertrain Control Module instead of an ECM or ECU. It’s important to know which one you have because a PCM controls all of the engine functions.
That’s important to know when you’re experiencing ECM failure symptoms as opposed to failures in other parts of your car’s powertrain. Otherwise, you may spend a lot of money trying to replace parts or fix systems that don’t need repair.
Or your car could choose to die at the most inconvenient time and place, like the middle of the expressway during rush hour.
What Causes ECM Failure?
An ECM is not just one of the most important computer components in your car today. It’s also one of the most expensive. A Cummins ECM, for example, costs more than $995.00.
The ECM gather data from all the sensors in your engine and uses this to determine when to fire the spark plugs and give the engine some gas. It also tells the injectors how much gas to pump.
Anything that breaks these connections and this flow of information will cause ECM failure. There is no real maintenance you can perform to ensure that your ECM lasts longer.
Here are some of the most common connection breakers. If you can spot these early enough, you can expect to pay half or than the cost of a new ECM to repair one.
Moisture and Corrosion
Not surprising, moisture and corrosion are behind most problems. Over time, changing seasons will eat away at seals and moisture will creep in. The ECM is unlikely to die immediately, which is why you’ll see so many of the symptoms of failure come and go.
Fuel Solenoid Shorts
Similarly, corrosion in the solenoid can lead to shorts that burn out the ECM. The fuel solenoid sits on top of the fuel pump, so if it shorts out, or the wire between it and the ECM is burned out, the ECM can be burnt out.
The third most common cause of ECM burn out is bad grounding. This can be the result of loose or corroded ground wires to the battery or the frame
Injection Wiring Harness
The other soft spot in the sensor connections is at the Fuel Injector Harness. Like the solenoid, a break in the wiring here can cause a short in the ECM. This is also another point of moisture entry over time.
Bad Jumps and Starters
There is very little you can do to protect your engine from the elements, but there are two other big causes of ECM failure that are caused by people.
The first is a reversal or incorrect cable connections during a car jump start. The second is replacing a bad starter with the wrong starter for your vehicle. Both these will instantly short out the ECM.
Dead Battery Cells
A failing battery can cause big issues in your ECM as well. Many times a dead battery cell is left in the rig long after it has died. This affects the grounding in the battery which in turn affects the ECM.
ECM Failure Symptoms
Here are some of the most common tip-offs that your car’s brain is what’s at fault and not necessarily the part it is trying to tell you is at fault. Keeping careful records of all the work you’ve had done on your car and when will help you flag some of these as suspicious.
Check Engine Light
The check engine light annoys and scares people. It comes on whenever your onboard computer detects a problem with any of its sensors or circuits.
Or it comes on and goes off randomly, or stays on despite a diagnostic of the trouble shows there is no problem.
Engine Stalls Or Misfires
Erratic engine behavior is another frustrating signal that your ECM may be going bad. The symptoms of stalling or misfiring may come and go and there may be no pattern discernible. What seems severe at one time may be very light the next time.
Erratic Engine Performance
Have you noticed lags in acceleration or timing issues?
These can all be symptoms of a faulty ECM. Changing to high-performance gasoline is not likely to have a positive effect despite TV commercials to the contrary.
A tune-up may actually mask a growing ECM problem for a while, but if bad idling continues after new plugs have been put in, that’s a strong ECM failure symptom.
Car Will Not Start
If you try to start it and nothing happens, you probably wouldn’t think of your ECM as the culprit right away. The same goes for that cranks but doesn’t turn over. Most likely you’re going to suspect a bad battery in this case.
Poor Fuel Consumption
Another symptom of possible ECM failure is poor fuel consumption. Bad fuel injectors and bad oxygen sensors are usually blamed for a car that suddenly burns more fuel than it needs. However, a brain that no longer tells the injector how much gas to push could be the real culprit.
Diagnosing ECM Failure
If your check engine light comes on, the error code may or may not indicate that the problem is in your ECM. If you’re fairly confident in your abilities to repair your own car, this is not one you want to do yourself.
What you can do is find and download the repair manual for your vehicle. When you know when to expect or how to spot normal powertrain issues, it can help you spot ECM failure symptoms.