U3036: Communication Authentication Signal Performance

What it means

Authentication signal arrives within tolerances but timing or content drifted from expected behavior.

At a glance

• Usually lights the warning light of the system that lost communication

How it works

Vehicle modules exchange authentication signals to verify network messages. This code sets when an authentication signal arrives but its timing or content has drifted outside expected behavior, which can cause intermittent message rejection or restricted functions.

Common causes

Most likely first.

1. Authentication timing drift
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 record whether the fault is intermittent or tied to particular operating conditions.
2. Review freeze-frame and live data for authentication status and timing when the fault occurs.
3. Inspect gateway and CAN wiring, connectors, power, and grounds for loose or corroded connections that could delay or corrupt messages.
4. Check for recent module programming or configuration changes that may have altered authentication timing or expected content.
5. If the physical network checks out, have gateway routing and module authentication timing checked with supported diagnostic procedures; verify termination against the manufacturer's specification.

Common fixes

• Secure or repair intermittent gateway and CAN connections.
• Restore correct module configuration or programming if timing expectations changed.
• Correct confirmed gateway routing or CAN termination faults.
• Repair or replace a module only if testing confirms it generates or receives out-of-tolerance authentication signals.

Can I keep driving?

If the vehicle drives normally, keep trips short and avoid relying on functions that become intermittent. Stop if the fault causes restricted operation or affects an essential control, and arrange diagnosis.