Guide To P0644 OBD Error Code Solutions

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P0644 is a diagnostic trouble code (DTC) for "Driver Display Serial Communication Circuit". It indicates that a malfunction has been detected between the PCM and one of the other supporting control modules. Due to this error code you might start facing problems like delayed acceleration, harsh shifting, rough idling etc. An inspection should be scheduled as soon as this code will be detected to avoid any serious issues in near future.

OBD-II Code Instrument cluster may not operate normally is defined as a Driver Display Serial Communication Circuit. Error code P0644 is detected when there is a communication problem between multiple control modules. Communication between the PCM and other on-board controllers is serial data communication. This means that single bytes of data are transferred sequentially - one byte at a time. All on-board serial data communication is carried out using the controller area network (CAN). CAN makes it possible to use a common set of controllers, sensors, and actuators, as well as one single type of diagnostic system (OBD-II). In the event of a loss of communication with (or lack of ability to control) any of the various supporting control modules is detected a trouble code will be stored and a service engine soon lamp will be illuminated.

What causes this problem with the Driver Display Serial Communication Circuit?

• Faulty driver display system
• Defective relay
• Poor electrical connection in PCM
• Faulty ground wire
• Inoperative electrical components in CAN Bus
• Faulty PCM

1. PCM -The Powertrain Control Module PCM is an on-board electronic control unit that primarily controls the charging, emission and transmission systems of the vehicle. It works in conjunction with a network of sensors, using their inputs to control the functioning of the engine and powertrain. Check out the PCM as well as any faulty or failed component of PCM can also create trouble codes.
2. Scanner - Scanner is one of the diagnostic tools used to diagnose the stored trouble codes. You may need this if you are diagnosing the trouble code by yourself.
3. Relay - A car relay is an electromagnetic switch that allows a person to run a higher current application than that which would normally exceed the capacity of a standard toggle switch. A defective relay should be replaced as soon as possible.
4. CAN Bus - Automotive Controller Area Network System. The Controller Area Network (CAN, also known as CAN Bus) is a vehicle bus standard designed to allow electronic control units and devices to communicate with each other in applications without a host computer. However, it rarely fails but it should be inspected as well and repaired or replaced if required.

Some common symptoms which help you identify the trouble code P0644 are listed below:

• Engine stalling at idle
• Harsh shifting
• Poor acceleration
• Decreased fuel economy
• Loss of driver display system

Due to this code you may face noticeable drivability issues so one should always inspect all the potential causes while diagnosing it so that you can repair or replace the inoperative components. Following repairs or replacements may help you to fix this code:

• Inspect all the related wiring and connectors and replace the faulty one.
• Check all the electrical connections in PCM and replace if necessary.
• Replace the electrical components in CAN bus.
• Inspect the ground strap or ground wire, if found loose or shorted then replace it.
• Update the PCM drivers.
• Replace the failed PCM or CAN bus (Rare Case).

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Diagnosing this code may require several tools and thorough inspection so it is always recommended that you should get your vehicle diagnosed by an experienced diagnostician. Steps to diagnose this error code are as follows:

• Use the scanner to view the freeze frame data and gather information about the P0644 code.
• Reset the trouble codes, restart the vehicle, and see if the P0644 code remains detected.
• If the code has disappeared, then an intermittent error or an inaccurate detection are likely to blame.
• If the code remains detected, then visually inspect the electrical components in the PCM and CAN bus.
• Any loose or corroded connectors, shorted wires, or blown fuses should be replaced.
• The ground strap and ground wire will then need to be tested.
• Hook up a specialized diagnostic CAN scanner, which provides detailed information about the control modules and circuitry. This scanner can be used to pinpoint where the problem that is causing the P0644 code is coming from.

Common Mistakes When Diagnosing the P0644 Code

Other trouble codes are usually present when the P0644 code is detected. Often, these codes are simply a reaction to a communication failure created by the P0644 code. If the codes are addressed out of order, a reactionary code may be erroneously inspected, and unnecessary repairs may take place.