P0644Generic code

P0644 Code: Driver Display Serial Communication Circuit

The P0644 code means the computer is not communicating correctly with the driver display or the instrument cluster. It does not hurt the engine, but dash information may be missing. The wiring is the usual suspect.

Severity
Low
Can I keep driving?
Yes, no immediate risk
Estimated cost
$0 to $500
Difficulty
Medium
System
Computer and Outputs
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0644 code means

Some vehicles send engine information to a display in the dash over a dedicated serial line. If that communication fails, the computer stores the P0644 code.

It is usually caused by the wiring or by the instrument cluster itself.

On heavy vehicles and some pickups, the driver display shows engine information (fuel use, warnings) that it receives over a serial line. If it fails, important warnings can disappear. Also check the cluster fuses and the display power supply before you suspect the module.

P0644 code symptoms

  • Dash information that is missing or wrong.

Likely causes of the P0644 code

  1. Communication wiring cut or with a loose contact.
  2. Instrument cluster or display with an internal fault.
  3. Loose or corroded connector.

How to diagnose the P0644 code step by step

  1. Check the wiring.
  2. Test the display.
  3. Check the cluster fuses and the display power supply.

How to fix the P0644 code

  • Repair the wiring or the display.

Technical reference data

  • Serial or CAN communication line.
  • Reference values: check the manufacturer data for your vehicle.

Brand-specific notes

This code shows up on some commercial vehicles and pickups that send engine data to the dash over a serial line.

If you own one of those, check the display power and fuses first, since that is quick and cheap.

Frequently asked questions about P0644

Can I drive with a P0644 code?
Yes. The engine itself is not affected, but you may lose some dash information, including warnings, so watch the gauges that still work.
Is it serious?
Not for the engine. The concern is that a warning you need might not show up on the display.
What usually fails?
The wiring. A cut wire or a loose contact in the communication line is the typical fault.
How much does it cost to fix P0644?
Between $0 and $500. A fuse or a connector costs little, and a replacement display or cluster costs the most.
What does the P0644 code mean?
It is a generic OBD2 code that means the serial communication between the computer and the driver display is not working.
What is the most common cause of P0644?
Damaged communication wiring or a bad connector. A P0644 code can also come from a fault inside the cluster.

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Questions about the P0644 code

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