Engine Control Module
The engine control module (ECM) or engine control unit (ECU) is basically a mini-computer that controls all the functions underneath the vehicle and inside the hood. This piece of technology offers plenty of advantages, but it's one of the trickiest automotive parts to diagnose and repair. This is because ECU problems usually come and go, and many of the actual signs of a faulty ECU may not seem like electrical issues at all. So to help you figure out the puzzle behind your car's engine control unit, here are the common signs of a problematic ECU:
Check engine light won't switch off even after a reset
If your car's check engine light keeps on flashing even if the system was just reset, then a bad ECU is to blame. So better bring your vehicle to a shop and have a professional check on the control unit as soon as possible.
A faulty engine control module can make the alternator undercharge or overcharge the battery. But before you put the blame on the ECU, check first if the cables and the actual battery aren't damaged. If everything checks out, then it means the alternator is receiving faulty instructions from a malfunctioning ECU.
Unexplained starting problems
If the engine suddenly won't start and you've already checked the battery and other electrical components but they're all working fine, then the ECU is probably the culprit. A faulty control module can send mixed-up signs to the various ignition parts, preventing the engine from starting up.
Another sign of a faulty engine control module is experiencing unexplained transmission issues. This is especially true if your car has an automatic transmission; this type of transmission relies on the control module when shifting gears. So if you experience sudden jerking and stopping even if your transmission assembly is properly maintained and has enough transmission fluid, the usual suspect is a bad ECU.
Poor emissions results
A faulty ECU can send wrong signals to the engine, causing it to function poorly and result in bad emissions. If the engine, oil levels, and emissions filter are all in good condition upon checking, you better take a look at the ECU.
Diagnosing an ECU
Whenever you experience any of the problems discussed above, you should always check first the engine control module by using an on-board diagnostics tool. There are some issues, however, that can't be diagnosed with this tool. If this is the case, it's time to bring your car to the shop and have a mechanic take a closer look.
Because many of the symptoms of a faulty engine control module mimics the signs of other car problems, diagnosing the cause of the problem can get confusing. The trick here is to rule out first all other possible culprits. Once all the other parts are checked and are working properly, it's time to check on the ECU. Depending on the condition of your damaged ECU, it might need minimal repair, a simple reset, or a complete replacement. If it has to be replaced, get a new one as soon as possible since all your car's functions rely on this little piece of plastic.