GENERAL INFORMATION
Description
The Engine Control Module (ECM) utilizes integrated circuitry and information carried on the Controller Area Network
(CAN) data bus along with many hard wired inputs to monitor many sensors and switches inputs throughout the
vehicle. In response to those inputs, the internal circuitry and programming of the ECM allow it to control and inte-
grate many electronic functions and features of the vehicle through both hard wired outputs and the transmission of
electronic message outputs to other electronic modules in the vehicle over the CAN data bus.
The following are the input and output components monitored by the ECM. The monitored functions include compo-
nents from the engine, ignition, transaxle, air conditioning, or any other ECM supported subsystem.
ECM Inputs
• Brake Switch Sensor
• A/C Pressure Switch
• Camshaft Position (CMP) Sensor
• Crankshaft Position (CKP) Sensor
• Engine Coolant Temperature (ECT) Sensor
• Intake Air Temperature (IAT) Sensor
• Air Flow Sensor
• Throttle Position Sensor (integral with Electronic Throttle Control Actuator)
• Power Steering Switch
• Accelerator Pedal Position (APP) Sensor
• Knock Sensor
• Oxygen Sensor (Upstream & Downstream)
• Clutch Pedal Switch (manual transaxle only)
ECM Outputs
• Canister Control Valve
• Fuel Injectors
• Fuel Pump Relay
• Electronic Throttle Control Actuator
• Ignition Coil
• A/C Compressor
• Cooling Fan
• Oxygen Sensor heating coil (Upstream & Downstream)
Operation
The ECM monitors components and circuits and tests them in various ways depending on the hardware, function,
and type of signal. For example, analog inputs such as throttle position or engine coolant temperature are typically
checked for opens, shorts and out-of-range values. This type of monitoring is carried out continuously. Some digital
inputs like vehicle speed or crankshaft position rely on rationality checks - checking to see if the input value makes
sense at the current engine operating conditions. These types of tests may require monitoring several components
and can only be carried out under appropriate test conditions.
The ECM is a pre-programmed, microprocessor-based digital computer. It regulates ignition timing, air-fuel ratio,
emission control devices, charging system, certain transmission features, speed control, air conditioning compressor
clutch engagement and idle speed. The ECM can adapt its programming to meet changing operating conditions.
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