Principle Of Operation
Battery Voltage is monitored by the ECM for fluctuations. It will adjust the output functions to compensate for a lower (6v) and higher (14v) voltage value. For example, the ECM will:
- Modify pulse width duration of fuel injection.
- Modify dwell time of ignition.
When KL15 is switched "on" the ECM is ready for engine management. The ECM will activate ground to energize the Engine Control Module Relay. The Engine Control Module Relay supplies operating voltage to the ECM and the previously mentioned operating components. MS43 - Five seconds after the ignition is switched on and the voltage at the KL15 input is <9 volts, the ECM compares the voltage to the ECM Relay supplied voltage. If the voltage difference between the two terminals is greater than 3 volts, a fault code will be set.
When KL15 is switched "off" the ECM operating voltage is removed. The ECM will maintain a ground to the Engine Control Module Relay for a few seconds to maintain ignition coil activation (MS43 Emission Optimized).
Ground is required to complete the current path through the ECM. The ECM also:
- Internally links a constant ground (1) to the Engine Sensors.
- Switches ground (2) to activate components.