The average Joe may find the ECU boring. To US, it’s interesting! We offer good used guaranteed units for sale to the customer at a very very high value for dollar, often times saving customers 900% over the new part price. Firstly, Every ECU (Electronic control unit) for every make, model & trim level car is different. Many times, there are even many different units for the same exact year and make car depending on where in the world it was sold, what emission system equipment it came with, what transmission it has, what assembly line it was produced on, etc. The part number MUST match your original part number for the ECU to work correctly. There are some exceptions to this but this is generally the rule.

The ECU, also known as an PCM, ECM, DME, or simply “control unit” is a complex microprocessor electronic control device. These units cost manufacturers hundreds of dollars per vehicle, with initial production costs in the millions of dollars! This is why these often times cost several thousand dollars for a new replacement ECM from the manufacturers. Even though there may be only a few hundreds of dollars worth of components, they are trying to differ their initial investment. If the ECM you are looking for is for a low production vehicle these costs can skyrocket and the difficulty of finding a correct unit for your car from anyone but the manufacturer rises dramatically.

Why would they go wrong? There are many cars that will last their entire lifespan with their original ECU and never have a hiccup. Other cars have a near 100% failure rate by the time they are 15 years old. The 1989 Saab 900 models come to mind. Most are somewhere in the middle. Many times the initial ECU design is flawed and a manufacturer comes up with a revised unit that has a significantly better lifespan. Other times an individual situation such as a solder joint that was never as good as it should have been from new, fails once it hits a certain age. Sometimes internal corrosion is the issue… Other times wiring faults such such as a short circuit or a bad alternator can cause a failure. Also, The ECU’s internal “ROM” does not have an indefinite lifespan either. Typically ROM can store data (such as a cars fuel maps) 100% reliably for approximately 30 years. Occasionally, and possibly by external factors such as heating and cooling cycles, this can potentially be dramatically reduced. Other times, there are no identifiable reasons as to why a failure has occurred, it “just happened”

What does it do? Quite simply the ECU is the brain of the car. Everything related to the engine control, and sometimes more is done here. The ECU has data stored in it’s ROM (Read only memory) system which the ECU’s internal CPU (central processor unit) uses to calculate the amount of fuel to inject based on sensor inputs. The CPU is where the data is processed. The ECU’s CPU uses the sensor inputs and the data stored in the ROM, to calculate the amount of fuel to inject turn on the fuel pump, run the emissions equipment, and all other external devices connected to it. This makes it quite clear why this device is so critical.

Also, on many newer cars (typically 2005 and newer), these ECU’s are “married” to the original car they were installed in at the factory. The reason for this is increased theft deterrence, to deter after-sales, and to decrease the likely hood of the wrong ECU being installed into the wrong car. While this does deter after-sales, it does not prevent it! As long as the vehicular VIN is provided along with the used ECU for which is it programed, it can be re-programed to work in ANY car – provided the part numbers match. We offer full VIN programing on all SAAB ECU’s that require it. Dealerships also have this capability as well, but sometimes require a bit of arm twisting to get them to do this for you, as they would rather you to buy a NEW ECU from them… at probably 10X the price. A simple VIN-program will only get them about 1/2 hour labor from a customer. In time ePartsland hoped to be able to offer more VIM programing so you can avoid this trip to the dealer with newer cars.