P0644
Driver Display Serial Communication Circuit
Module communication
Generic OBD-II
High
What it means
P0644 means the ECM has lost or corrupted serial communication with the driver display (the instrument/message display). The engine still runs, but the display can go blank, freeze, or show wrong readings, so you may lose gauges and warning messages. It usually traces to the communication wiring, a connector, or the display module.
High
Can I keep driving? Usually drivable — the engine runs, but the driver display may go blank or show wrong data, so you can lose gauges and warnings. Treat missing instrumentation as a safety concern.
Common symptoms
What you'll notice
- Check-engine light on
- Driver display blank, frozen, or showing incorrect information
- Missing gauges or warning messages
- Intermittent display dropouts
Common causes
Most likely first
- Damaged or shorted wiring in the serial communication circuitLikely
- Loose or corroded connectors at the display or ECMCommon
- Failed driver display / instrument clusterCommon
- Poor power or ground to the display moduleLess often
- ECM fault (checked last)Less often
How to diagnose & fix
Work through it in order
- Scan all modules for related communication (U-series) codes to see which end has dropped off the bus.
- Inspect the wiring and connectors between the ECM and the driver display for damage, corrosion, or a poor fit.
- Verify the display module has good power and ground.
- Repair the communication wiring; replace the display/cluster if it's confirmed unresponsive with good wiring.
- Clear the code and confirm the display shows correct data.
FAQ
Quick answers
Is it safe to drive with P0644?+
The car will run, but losing gauges and warning lights is a real safety issue — you may miss a temperature or oil warning. Get the display fixed soon.
Can I just clear P0644?+
It clears, but returns while the communication link is broken. Repair the wiring or display to fix it properly.
Related codes
Often seen with P0644
Read & clear P0644 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX