Error Code P0650 is defined as Malfunction Indicator Lamp (MIL) Control Circuit Malfunction. This means there’s an issue in the computer output circuit, which can be likely caused by a defective electrical circuit or bulb.

This error code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II system, or vehicles made since 1996 up to present. Specifications on the definition, troubleshooting and repairs of course, vary from one make and/or model to another.

Definition

Error Code P0650 is stored when the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) or other supporting control module has determined a problem or failure with the control circuit of the malfunction indicator lamp (MIL also known as Check Engine light or Service Engine Soon light). This happens when the PCM senses voltage present in the lamp that is too high or too low. By monitoring the ground circuit, the PCM controls this lamp and checks the voltage on that ground circuit.

The malfunction indicator lamp of a vehicle tells the driver about the potential problem with the vehicle. When it is not working properly, the driver may be using the vehicle unaware of the present problems, or it may become present during operation.

Note though that, it is a normal operation for the MIL to light up for a few seconds and the go out when the vehicle is started or the vehicle’s ignition is turned.

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Common Symptoms

This code doesn’t cause drivability symptoms. However, since the problem is in the Check Engine light itself, the Check Engine light will show some errors. Unlike other error codes, Error Code P0650 causes the Check Engine light to either NOT light up, or the Check Engine light will be illuminated all the time. The symptoms vary depending on the conditions. Some of the variations are:

  • Check Engine light won’t turn on even if there’s a problem present
  • Check Engine light is on even when there is NO problem present

Possible Causes

There are many factors that can cause this error code, such as:

  • Open, shorted, damaged, or corroded wiring and related electrical components in CAN bus harness
  • Damaged or defective MIL bulb or LED
  • Damaged or defective MIL circuit
  • Damaged or defective CAN bus
  • Defective or damaged PCM

How to Check

There are many ways and methods to diagnose this code, but the most common process most technicians use is:

They start by using an OBD-II scanner to check for stored Error Code P0650

Next, they check whether the lamp turns on for a few seconds when vehicle starts and it turns off shortly after

Then, they check whether the bulb is burnt or not

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Next, they ensure the bulb is seated correctly, with a proper electrical connection

Then, they inspect the wiring and electrical connections and look for signs of corrosion or damage

They separate connectors and check for bent pins, broken terminals or corrosions that may be causing the error code

Then they check for a burned out MIL fuse

Lastly, they use the DVOM (digital volt-ohmmeter) to check for shorts to ground or open circuits

How to Fix

Repairs for this error code include:

  • Replace burned out or damaged bulb or LED
  • Seat bulb properly for the right electrical connection
  • Replace corroded and damaged wiring and other related electrical connectors
  • Repair or replace damaged terminals
  • Straighten bent pins
  • Replace burned out fuses
  • Replace defective PCM (rare condition)

It is important to always diagnose properly and repair trouble codes in the order they appear. This is because subsequent codes can be a symptom of a problem higher above. And this is usually the case for Error Code P0650, which can simply be a symptom of a bigger problem.