P0650 GMC - Malfunction Indicator Lamp Control Circuit Malfunction
- Malfunction Indicator Lamp Bulb harness is open or shorted
- Malfunction Indicator Lamp Bulb circuit poor electrical connection
- Faulty Engine Control Module (ECM)
A voltage is supplied directly to the malfunction indicator lamp (MIL). The Powertrain Control Module (PCM) controls the lamp by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component ON, the voltage of the control circuit should be near 0 volts. When the PCM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage.