IDM Explained

Jeep 2.5 Liter, four-cylinder engine, chromed....

Jeep 2.5 Liter, four-cylinder engine, chromed. This picture of the display engine shows part of the fuel injection system (with MPFI). The fuel rail is connected to the injectors that are mounted just above the intake manifold. This engine was developed by American Motors Corporation (AMC) and continued to be manufactured by Chrysler. All were built in Kenosha, Wisconsin. (Photo credit: Wikipedia)

A driver supplies the proper voltage to the solenoids on the fuel injectors of a Ford Powerstroke Engine. The 7.3 Ford Powerstroke Diesel uses an Injector Drive Module (IDM). The voltage provided by the IDM is critical to the performance of the fuel injectors, and therefore, the engine itself.

You should be aware that the 6.0 Ford Powerstroke diesel utilizes an Injector Control Module (ICM).

Prior to 1999, these engines used a 110 volt driver. The 1999 and newer engines utilize a 120 volt injector drive module. This voltage is crucial to the performance of the fuel injectors, and thus, the engine itself. The part may interchangeably be called a Fuel Injection Control Module (FICM).

You can reach the IDM through the driver’s side fender. You will need to remove the fender liner to get to the IDM. Due to its location in the wheel well corrosion is oftentimes a problem. You should check the connections for any corrosion at this time.

Problems resulting from a defective IDM producing low voltage can be challenging to pin down. The engine may still run, but not run well with low voltage. When the voltage reaches a minimum, the engine will stop.

You may check the output voltage on the ICM by removing the bolts on the cover. Once the cover is off, use the screw under the cover as the positive. When checking the IDM it is also a good opportunity to check for corrosion in and around the IDM, its connections and at the wiring harness. To check the condition of the harness, pull on it slightly while the engine is running. If you notice a change in the engine’s operation when you tug, it is likely there is a problem with the harness. The only fix for a bad harness is to replace it.

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