U012F: Lost Communication With Generator B Control Module

What it means

Lost Communication With Generator B Control Module: the control module has detected this fault condition.

At a glance

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

How it works

Generator B Control Module monitors or manages generator B and shares status with other controllers through the vehicle communication network. This code sets when a controller stops receiving the expected messages from generator B’s module, which can result from lost module power, a network fault, or incorrect gateway routing.

Common causes

Most likely first.

1. Module unpowered
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 information and scan all modules for communication, charging, or electrical-system faults; see whether Generator B Control Module is the only module that does not respond.
2. Check battery and charging-system condition, then verify the module’s fuses, power feed, and grounds using the vehicle wiring diagram.
3. Inspect the Generator B Control Module connector and nearby CAN wiring for corrosion, loose pins, moisture, or damage.
4. Use a scan tool to check module response and confirm whether the gateway recognizes and routes generator B messages.
5. If power and ground are correct, test CAN wiring and termination according to the manufacturer’s procedure and specification before replacing parts.

Common fixes

• Correct low battery or charging voltage if it is affecting module communication.
• Repair a blown fuse, poor ground, or damaged power feed to Generator B Control Module.
• Repair or clean a loose, corroded, or damaged module connector.
• Repair an open, short, or damaged CAN wire on the module’s network path.
• Fix a verified gateway routing issue or replace the module only after its supply and network test correctly.

Can I keep driving?

If charging or electrical warnings appear, limit driving and avoid relying on systems that may depend on generator B; stop if the vehicle loses power or becomes unreliable. Prompt diagnosis can prevent an electrical fault from leaving other controllers without generator status.