U3035: Communication Authentication Signal Invalid Data

What it means

The received authentication signal contains invalid data — message authentication code does not match expected value, suggesting tampering or corruption.

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

Vehicle modules authenticate certain network messages by checking a code attached to each message. This code sets when the received authentication data does not match what the receiving module expects, so the message may be rejected and related functions restricted.

Common causes

Most likely first.

1. Authentication code mismatch
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

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 for authentication and communication codes, and note which messages or modules report invalid data.
2. Save freeze-frame and live data before clearing codes to see whether the error is persistent or limited to a particular event.
3. Check for recent module programming, replacement, or configuration changes that could have caused mismatched authentication data.
4. Inspect gateway and CAN wiring, connectors, power, and grounds for intermittent faults or damage.
5. If wiring is sound, check gateway message routing and module authentication status using supported procedures, and assess CAN termination against the manufacturer's specification.

Common fixes

• Correct module configuration or programming that caused an authentication mismatch.
• Repair damaged, loose, or corroded gateway or CAN connections.
• Correct a confirmed gateway routing or CAN termination fault.
• Reprovision or replace a module only if testing confirms its authentication data is invalid or cannot be validated.

Can I keep driving?

Treat this as a potentially security-related communication fault: avoid driving if the vehicle enters limp mode or loses an essential function. Do not rely on any affected assistance or safety features, and arrange prompt diagnosis.