U3502: Control Module Input Power A Circuit High

What it means

Input power line A voltage above expected range — typically charging system overvoltage. A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.

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

The module monitors its A input-power feed to confirm the voltage stays within its allowed range. This code sets when that feed is higher than expected, which can disrupt the module or its communication with other modules.

Common causes

Most likely first.

1. Alternator regulator failed (overvoltage)
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. Record freeze-frame data and scan all modules for voltage and communication codes to see whether the fault coincided with system-wide overvoltage or a loss of this module.
2. Check battery condition and charging-system output, since a failing alternator regulator can raise voltage across the vehicle.
3. Inspect the named module’s A power-feed connector, wiring, fuse, and ground for damage, poor contact, or signs of overheating.
4. Measure voltage at the A feed and compare it with the manufacturer's specification, including while the fault is present.
5. If supply voltage is normal, follow the vehicle wiring diagram to check the gateway’s routing and CAN network integrity, including termination as specified by the manufacturer.

Common fixes

• Clean and secure a poor connection at the A feed or its ground.
• Repair damaged A-feed wiring or replace a faulty fuse or terminal.
• Repair or replace an alternator regulator if charging voltage is above specification.
• Repair the gateway or CAN network fault if power at the module is correct.

Can I keep driving?

If warning lights multiply, the module shuts down, or the vehicle enters limp mode, avoid continued driving and arrange a safe stop; overvoltage can damage electronics and impair vehicle functions. If symptoms are absent, limit driving to a short trip for diagnosis and stop if drivability or electrical functions change.