All vehicles making use of fuel injection have either engine control modules or programmable control modules. The engine control module (ECM) makes use of inputs from different sensors to pass on information to other sensors as well as components. The ECM typically closes a ground circuit so that a component, like a fuel injector, can be enabled. The ECM also calculates the temperature of the engine by the means of the coolant temperature sensor in order to adjust the timing as required. It also calculates the placement of the throttle by the means of throttle position sensor and even calculates the barometric pressure of the outside air so that necessary adjustments will be made.
If you want to replace an ECM, the battery ground cable should be loosened with a wrench and the cable should be set aside, making sure that it does not touch any metal. Static electricity in your body should be discharged by grounding yourself against a metallic object. This grounding must be taken seriously because the slightest bit of static electricity from your body is harmful to the module.
You should then access the vehicle’s ECM and its location is dependent on the year, model and make of the vehicle. It can be located under the passenger floorboard, behind the passenger side kick panel, under one of the seats or in the engine compartment. The manual of the vehicle will be a great source of help in this regard and it should be consulted appropriately.
Furthermore, the module should be pulled out of the vehicle. Majority of them are installed in a bracket which requires simply unbolting the holding bolts with the right socket or wrench. The module should then be pulled out far enough so that the plugs at its back can be removed. The plugs should be removed and it is important to note that some plugs are held in by plastic tangs while others have a bolt in the center of them, besides the plastic tangs.
The cover of the ECM should be removed if you only want to replace the PROM. The PROM should be taken out with your hand and replaced with a new one. You should ensure that all the pins are lined up so that they will not bend and thereafter, you should replace the cover. The wiring harness plugs should be plugged into the back of the ECM making sure that the prongs are not bent. The plugs should be snapped to place while the bolts should be installed. You should then reinstall the module into its bracket and replace the carpet as well as trim molding.