Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Control Module Communications
The control module system has a computer, the powertrain control module (PCM), to control fuel delivery, timing, and some emission control systems. The control module system monitors a number of engine and vehicle functions and controls the following operations:
- Fuel control
- Fuel injection timing
- Exhaust gas recirculation (EGR)
- Transmission shift and shift quality functions
- Specific transmission control diagnostics are covered in Transmissions.
The diesel powertrain control module (PCM), located in the passenger compartment, is the control center of the control module system. The powertrain control module used on the electronic fuel injected 6.5L diesel is referred to as a PCM.
The PCM constantly looks at the information from various sensors, and controls the systems that affect vehicle performance. The PCM performs the diagnostic function of the system. The PCM can recognize operational problems, alert the driver through the malfunction indicator lamp (MIL) Service Engine Soon, and store one or more diagnostic trouble codes (DTCs) which identify the problem areas to aid the technician in making repairs. See the specific diagnosis procedure for more information.
The PCM processes the various input information and sends the necessary electrical responses to control fuel delivery, timing and other emission control systems. The input information has an interrelation to more than one output, therefore, if the one input failed it could effect more than one systems operation.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.