P0650 OBD-II: Malfunction Indicator Lamp (MIL) Control Circuit

What Does P0650 Code Mean?

OBD-II Code P0650 is defined as a Malfunction Indicator Lamp (MIL) Control Circuit Malfunction

The purpose of the Check Engine Light, technically known as the Malfunction Indicator Lamp or (MIL), is to alert the vehicle's driver that it's emissions control system is malfunctioning and that the vehicle is now polluting the air. The light comes on whenever the vehicle's pollution levels are 150% or greater than the EPA mandated levels for that year, make and model.

Code P0650 Indicates that the circuit that controls the illumination of the Malfunction Indicator Lamp has failed its self-test. This self-test occurs every time the key is inserted into the ignition and rotated to the start position. When this happens, the MIL light should illuminate and when the engine starts, the MIL light should stay on for 1-3 seconds and then go out. During this time frame, the PowerTrain Control Module checks the performance of the MIL circuitry by looking at various volage readings.

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The PCM or Power Train Control Module performs many vital functions in a modern vehicle, such as management of the Emissions Control Systems, Fuel System, Ignition System, Transmission, Anti-Lock Brake and Traction Control systems.

P0650 Symptoms

• Check Engine Light will illuminate
• Failure of Emissions Inspections due to MIL malfunction
• In many cases, there are no adverse conditions noticed by the driver

Common Problems That Trigger the P0650 Code

• Malfunction of the MIL driver in the PCM
• Defective wiring/connection in the MIL wiring harness
• Defective MIL ground circuit(s)

Common Misdiagnoses

• PCM is replaced when the root cause is defective wiring
• PCM is replaced when the root cause is a defective instrument cluster circuit board

P0650 Diagnostic Theory for Shops and Technicians

When diagnosing a P0650 code, it is important to record the freeze frame information and then duplicate the code setting conditions with a test drive at the recorded freeze frame conditions. Carefully watch the serial data stream PID values of MIL command and MIL actual. If they disagree at anytime, then you may have verified the problem. I always remove the bulb from the Instrument Cluster and verify the power source, the PCM provides the ground. I do this because the root of the problem may the Instrument Cluster itself. It never hurts to scan the data and codes for the Instrument Cluster and the BCM or Body Control Module. Study the applicable wiring diagram and verify the existence of excellent continuity between the PCM and the Instrument Cluster and MIL socket.