A vehicle's electrical control module measures and controls the changes within the motor of a combustion engine. The vehicle's ECM wiring diagram is used to map the source of electrical errors within the ECM, allowing individuals to correct common electrical problems.
The ECM is a computerized system that monitors the change in voltage coming from sensors distributed throughout a vehicle. Sensors relay information, such as change in engine coolant temperature and crank position. The ECM supplies a specific amount of voltage to power each sensor and receives a voltage feedback. The computer module registers an excessive increase or decrease in the voltage as an error and displays a code and/or a Check Engine light.
The error codes are used together with an ECM wiring map to solve the electrical issue. Since each sensor feeds into the ECM as a simple circuit and through a single pin, the ECM wire diagram can be used to map the source of the error. Each error code refers to a single circuit and names the condition, such as a reduced coolant temperature, but does not provide a cause. The vehicle owner or technician must check the sensor location to determine the cause or if the ECM is reading a false error.