U3024: Control Module Input Power Circuit B - Ignition Input On/Start Circuit Correlation

What it means

Control Module Input Power Circuit B - Ignition Input On/Start Circuit Correlation: the value does not correlate with the related sensor or expected pattern.

At a glance

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

How it works

Input power circuit B supplies a control module through an ignition ON/START path. The module checks whether circuit B's supply state agrees with the related ignition input and sets U3024 when those signals do not correlate. This mismatch can interrupt the module's operation or communication.

Common causes

Most likely first.

1. Wiring or relay fault
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. Save freeze-frame data and scan for power-supply, ignition-input, and communication faults to identify when circuit B lost correlation.
2. Compare circuit B supply and the module's ignition ON/START state in live data while switching the ignition on and starting the vehicle.
3. Inspect circuit B wiring, its relay and fuse connections, and grounds for corrosion, looseness, heat damage, or a poor splice.
4. Test the circuit B supply path through the ON and START states, checking for dropouts against the manufacturer's specification.
5. If circuit B supply and ignition input agree at the module, check gateway reporting and CAN network termination against the manufacturer's specification.

Common fixes

• Clean and secure circuit B power, ground, or relay connections.
• Repair damaged wiring or a poor splice in the circuit B ignition supply path.
• Replace a relay or repair a fuse connection only if testing confirms a fault during ON or START.
• Correct a confirmed gateway reporting or CAN network fault if circuit B supply and input signals test correctly.

Can I keep driving?

A circuit B power mismatch can make the module drop out during starting or ignition changes, interrupting dependent functions. Stop driving if this affects a safety-related system or causes unpredictable vehicle operation.