VC Output Circuit: Description
The ECM constantly produces 5 V from the battery voltage supplied to the +B (BATT) terminal to operate its microprocessor. The ECM also provides this power to the sensors through the VC output circuit.
When the VC circuit is shorted, the microprocessor in the ECM and sensors that are supplied power through the VC circuit are inactivated because the power is not supplied from the VC circuit. Under this condition, the system does not start up and the MIL does not illuminate even if the system malfunctions.
HINT:
Under normal conditions, the MIL is illuminated when the engine switch is turned on (IG). The MIL goes off when the engine is started.