U044A: Invalid Data Received From Serial Data Gateway Module D

What it means

A receiving module detected implausible data from serial data gateway D. Bridged messages between sub-buses (CAN/LIN/FlexRay/Ethernet) fail plausibility checks and are rejected.

At a glance

• Usually lights the warning light of the system that lost communication
• The engine or gearbox may go into limp mode

How it works

A receiving module checks data passed through serial data gateway module D, which bridges messages between vehicle data networks. U044A sets when the receiving module rejects a gateway D message as implausible; the code alone does not show whether the original data, gateway, or network path is at fault.

Common causes

Most likely first.

1. Module internal fault or sensor input drift
2. Software version mismatch after replacement
3. Gateway module routing CAN messages incorrectly

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Scan all modules and save freeze-frame and communication data to identify the reporting module and any faults on the networks connected through gateway D.
2. Identify the functions affected and compare their actual state with the data reported by the receiving module.
3. Inspect gateway D connectors, power and grounds, and accessible network wiring for damage, loose terminals, or corrosion.
4. Use a scan tool to compare the relevant data on the source and receiving sides of gateway D, where the vehicle’s data access allows it.
5. Check whether recent module replacement or programming introduced a software or configuration mismatch across the bridged networks.
6. Test gateway D power, grounds, and applicable network circuits using the wiring information and manufacturer’s specifications.

Common fixes

• Repair damaged or poorly seated gateway D connectors or network wiring.
• Repair a confirmed power or ground fault at serial data gateway D.
• Correct software compatibility or configuration issues across the modules linked by gateway D.
• Repair a network fault on the affected side of the gateway identified by circuit testing.
• Replace or reprogram gateway D only if testing confirms an internal fault or corrupted software.

Can I keep driving?

Because this fault can disrupt data shared across vehicle networks, avoid driving if it affects essential controls, braking, steering, or visibility. If only nonessential features are affected and the vehicle behaves normally, drive cautiously to have it diagnosed.