Engine Control Module (ECM)

Fig.2 Diesel ECM:

ENGINE CONTROL MODULE
The Engine Control Module (ECM) is bolted to the left side of the engine below the intake manifold.

The main function of the Engine Control Module (ECM) is to electrically control the fuel system on vehicles equipped with diesel engines. The Powertrain Control Module (PCM) does not control the fuel system.

The ECM can adapt its programming to meet changing operating conditions. If the ECM has been replaced, flashed or re-calibrated, the ECM must learn the Accelerator Pedal Position Sensor (APPS) idle voltage. Failure to learn this voltage may result in unnecessary diagnostic trouble codes. Refer to ECM Removal/Installation for learning procedures.

The ECM receives input signals from various switches and sensors. Based on these inputs, the ECM regulates various engine and vehicle operations through different system components. These components are referred to as ECM Outputs. The sensors and switches that provide inputs to the ECM are considered ECM Inputs.

NOTE: ECM Inputs:

- Accelerator Pedal Position Sensor (APPS) Volts
- APPS1 Signal - For off engine APPS
- APPS2 Signal - For off engine APPS
- APPS Idle Validation Switches #1 and #2
- Battery voltage
- Camshaft Position Sensor (CMP)
- CCD bus (+) circuits
- CCD bus (-) circuits
- Crankshaft Position Sensor (CKP)
- Data link connection for DRB scan tool
- Engine Coolant Temperature (ECT) sensor
- Ground circuits
- Fuel Pressure Sensor
- Battery Temperature
- Fan speed
- Inlet Air Temperature Sensor/Pressure Sensor
- Intake Air Temperature Sensor/MAP Sensor
- Oil Pressure SWITCH
- Power ground
- Sensor return
- Signal ground
- Water-In-Fuel (WIF) sensor

NOTE: ECM Outputs:

After inputs are received by the ECM, certain sensors, switches and components are controlled or regulated by the ECM. These are considered ECM Outputs. These outputs are for:
- CCD bus (+) circuits
- CCD bus (-) circuits
- CKP and APPS outputs to the PCM
- Data link connection for DRB scan tool
- Five volt sensor supply
- Fuel transfer (lift) pump
- Intake manifold air heater relays #1 and #2 control circuits
- Malfunction indicator lamp (Check engine lamp) (databus)
- Oil Pressure Switch/warning lamp (databus)
- Fuel Control Actuator
- Wait-to-start warning lamp (databus)
- Fan Clutch PWM
- Water-In-Fuel (WIF) warning lamp (databus)