U012B: Lost Communication With Chassis Control Module B

What it means

ECU lost CAN communication with chassis control module B (vehicle dynamics). 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

Chassis Control Module B exchanges vehicle-dynamics information with other modules over the CAN network. This code sets when a module expecting those messages stops receiving them, often because Module B has lost power or ground, the network path is disrupted, or a gateway is not routing messages correctly.

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 the scan-tool report and freeze-frame data, then check whether other modules also report lost communication with Chassis Control Module B to distinguish a module-specific fault from a wider network problem.
2. Check the battery and charging system, then inspect Module B’s power and ground fuses, connections, and grounds for looseness, corrosion, or damage.
3. Inspect the Module B connector and accessible CAN wiring for water intrusion, bent pins, chafing, or an open or short.
4. Use a scan tool to check whether Module B responds and whether the gateway reports or routes messages from it; compare results with the vehicle’s wiring information.
5. If power and ground are sound, test the CAN network and termination according to the manufacturer’s procedure and specification before suspecting the module.

Common fixes

• Restore a weak battery or repair a charging-system fault affecting module voltage.
• Repair a blown fuse, poor ground, loose connector, or damaged power feed to Chassis Control Module B.
• Repair damaged CAN wiring or a connector fault on the module’s network path.
• Correct a gateway configuration or routing fault if network tests identify one.
• Replace Chassis Control Module B only after its power, ground, network connection, and gateway path have been verified.

Can I keep driving?

Drive cautiously only if steering, braking, and stability functions feel normal and no safety warning indicates they are unavailable; avoid high speeds and slippery roads. If chassis or stability functions are impaired, stop somewhere safe and arrange inspection, since other systems may also lose data or enter a limited mode.