The injector driver module (IDM) applies 115volts DC to all of the fuel injectors on the 7.3L DIT diesel engine. The IDM receives signals from the PCM for cylinder identification and fuel delivery command. The PCM controls when the timing of the injectors should start and how long the injector is open. The IDM controls the injector firing sequence through output drivers. The IDM has an output driver for each injector: one low side driver for each injector and one high side injector for each bank of injectors. The injector is fired when the output driver closes the circuit to ground.
Also referred to as the Fuel Injector Control Module (FICM).
The FICM requires a 12-volt power source. The FICM receives power from the vehicle batteries through the FICM relay contacts each time the key is turned to the ON position. As the key is turned to the ON position, the FICM provides an internal ground to the coil side of the FICM relay. This closes the relay contacts and provides the FICM with the necessary power. The PCM communicates with the FICM using the CAN protocol. The CAN protocol is an international standards organization (ISO) standard for serial data communication. The CAN protocol standard includes a physical layer using differential transmission on a twisted pair of wires and a data link layer that defines different message types, arbitration rules for bus access, methods for concern detection and concern confinement. The FICM receives information from the PCM, including the volume of fuel desired, RPM, engine oil temperature, injection control pressure, and others. The FICM uses those signals to calculate fuel injection and duration. After calculating injector fuel delivery time, the FICM sends 48 volts at a 20-amp pulse to the correct injector so that the correct amount of fuel is delivered to the cylinder at the correct time.
Removal & Installation
- Before servicing the vehicle, refer to the Precautions section.
Turn the ignition switch to the OFF position.
WARNINGNever remove the pressure relief cap while the engine is operating or when the cooling system is hot. Failure to follow these instructions can result in damage to the cooling system or engine or result in personal injury. To avoid having scalding hot coolant or steam blow out of the degas bottle when removing the pressure relief cap, wait until the engine has cooled, then wrap a thick cloth around the pressure relief cap and turn it slowly. Step back while the pressure is released from the cooling system. When certain all the pressure has been released, (still with a cloth) turn and remove the pressure relief cap. Failure to follow these instructions can result in personal injury.
- Relieve the cooling system pressure. Disconnect and plug or cap the engine vent hose and radiator vent hose.
- Remove the 2 bolts and position the degas bottle aside.
- Release the 2 exhaust pressure (EP) sensor harness pin-type retainers.
- Disconnect the EP sensor electrical connector and position the harness aside.
- Remove the fuel injector control module (FICM) nuts and bracket.
Remove the FICM bolts.
CAUTIONMake sure both latches are released before removing the electrical connectors or connector damage can occur.
Position out the FICM and disconnect the electrical connectors. Remove the FICM.
CAUTIONWith the engine cold, fill vehicles with a yellow fill level decal to within the yellow cold fill range shown on the decal. If the decal is missing, fill the degas bottle only to the molded line. The correct fill level on these vehicles is between the molded line and 15 mm (0.59 inch) below the line. These fill levels will allow for coolant expansion. Overfilling the degas bottle may result in damage to the pressure cap, which can cause the engine to overheat.
- To install, reverse the removal procedure.