P0644: Driver Display Serial Communication Circuit
What to do
Driveable, but treat displayed values with suspicion — a frozen temperature or fuel reading is worse than a blank one, because it looks trustworthy. Note exactly which readings are wrong or missing.
What this code means
A communication fault between the engine module and the driver's display. The instrument cluster or information display receives most of what it shows over the network — temperature, fuel level, range, service messages — so a fault here produces missing or frozen readings rather than a change in how the vehicle runs.
Worth noting which readings are affected, because a display missing everything points at the communication link while one missing a single value points further upstream at whatever supplies it.
Likely causes
Start here
- Damaged network wiring · specialist
- Corroded or loose connector · easy
Less common
- Failed instrument cluster · specialist
- Low system voltage disrupting communication · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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