P0644 Code: Meaning, Symptoms, Causes & Fix

Overview

Symptoms

• module not responding in scan tool
• intermittent no-start or limp mode
• multiple warning lights at once

Common causes

• Network termination or gateway fault affecting driver display serial communication circuit
• CAN bus wiring fault
• Connector pin damage/corrosion or harness stress near related components

How to diagnose P0644

1. Confirm P0644 and capture freeze-frame data with a professional scan tool.
2. Inspect wiring, connectors, and grounds related to driver display serial communication circuit for obvious defects.
3. Check CAN high/low integrity, network termination resistance, and module wake-up status.
4. Check for related DTCs to identify the root-cause chain before replacing parts.
5. After repair, clear codes and confirm readiness monitors complete without recurrence.

Severity of code P0644

Moderate: This code is moderate severity: the vehicle may still operate, but fault progression can increase repair cost over time.

Can you drive with P0644?

Most vehicles can be driven short-term with P0644, but postpone heavy load/highway driving until repaired.

If the warning lamp is flashing or drivability/safety is affected, avoid driving and diagnose immediately.

How to fix it (step-by-step)

1. Repair obvious wiring/connector faults first to prevent repeat parts replacement.
2. Address the root fault mode (communication) in the driver display serial communication circuit circuit/system.
3. Apply the required relearn/adaptation procedure if specified by service information.
4. Road-test and verify P0644 remains cleared under the conditions that originally set the code.

Fix options

• Repair CAN high/low wiring or termination issue.
• Scan all modules for communication chain faults.
• Clear DTCs and verify with live data and completed drive cycle.

Typical repair cost

$260-$1300

Common mistakes when diagnosing P0644

• Replacing parts without verifying voltage, ground, and signal integrity first.
• Ignoring related stored/pending codes that indicate upstream faults.
• Skipping post-repair verification drive cycle and readiness checks.

P0644 in common vehicles

P0644 appears across makes such as Mazda, Subaru, Lexus, Jeep. Failure patterns differ by platform: wiring routes, software calibration, and component supplier revisions can change root cause.

Frequently asked questions

What causes P0644?

P0644 is commonly set by communication faults affecting driver display serial communication circuit.

How much does it cost to fix P0644?

For P0644, repair costs are typically $260-$1300 depending on exact root cause, labor rates, and part quality.

Can I clear P0644 without repair?

You can clear P0644 temporarily, but the code usually returns until the underlying fault is corrected.

Helpful tools

• Estimate repair cost
• Decode your VIN
• Calculate fuel cost