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.
Operation - Diesel
The main function of the Powertrain Control Module (PCM) is to electrically control the fuel system. The PCM also controls the functions of transmission.
The PCM can adapt its programming to meet changing operating conditions.
The PCM receives input signals from various switches and sensors. Based on these inputs, the PCM regulates various engine and vehicle operations through different system components. These components are referred to as PCM Outputs. The sensors and switches that provide inputs to the PCM are considered PCM Inputs.
PCM Inputs:
- Accelerator Pedal Position Sensor (APPS) Signals No. 1 and No. 2
- Auto shutdown (ASD) sense
- Battery voltage
- Brake switch
- Camshaft Position Sensor (CMP)
- Charge Air Cooler inlet temperature sensor
- Crankshaft Position Sensor (CKP)
- Data link connection for a scan tool
- DEF level sensor
- DEF temperature sensor
- EGR Air Flow Control
- EGR cooler outlet temperature
- EGR Valve
- Engine Coolant Temperature (ECT) sensor
- Exhaust Gas Temperature sensors
- EATX module (if equipped)
- Fuel level
- Fuel pressure sensor
- Fan speed (engine cooling fan - via CAN bus)
- Generator (battery voltage) output
- Ground circuits
- Inlet air temperature sensor/pressure sensor
- Intake air temperature sensor/MAP sensor
- CAN C BUS (+) circuits
- CAN C BUS (-) circuits
- Key switch (ignition)
- NOx upstream and downstream SCR
- Oil Pressure switch
- Power ground
- SCR inlet temperature
- Sensor return
- Signal ground
- Soot sensor
- Turbocharger inlet exhaust temp sensor
- Turbocharger inlet exhaust pressure sensor
- Vehicle speed signal
- Water-In-Fuel (WIF) sensor
- Boost Pressure and Temperature Sensor
- Fuel Temp Sensor
- MAF Sensor
- Differential Pressure Sensor
PCM Outputs:
- A/C clutch relay
- Auto shutdown (ASD) relay
- Data link connection for diagnostic scan tool
- DEF pump and purging pump sensor
- DEF dosing valve
- DEF heater control module
- EGR air flow control
- EGR valve
- Fan clutch PWM (via CAN bus)
- Five volt sensor supply (primary)
- Five volt sensor supply (secondary)
- Fuel control actuator
- Fuel injector driver circuits
- Fuel transfer (lift) pump
- Generator field driver (-)
- Generator field driver (+)
- Intake manifold air heater relays No. 1 and No. 2 control circuits
- CAN C BUS (+/-) circuits for: speedometer, voltmeter, fuel gauge, oil pressure gauge/lamp, engine temp. gauge and speed control warn. lamp
- Malfunction indicator lamp (Check engine lamp). Driven through J1850 circuits.
- Oil pressure switch/warning lamp (databus)
- Wait-to-start warning lamp (databus)
- Water-In-Fuel (WIF) warning lamp (databus)
- Swirl Valve Actuator
- Throttle Valve Actuator and Position Sensor
- Crankcase Vent Heater
- EGR Cooler Bypass Valve
- Inlet Metering Valve
- Glow Plug Module
NO RELATED
Use the Manual With the Right Hardware
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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.