U007D: Control Module Communication Bus K Off

What it means

The control module communication bus K is off — the gateway has shut down or isolated this bus, often due to repeated bus errors or a "bus off" event in the CAN controller.

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

Bus K carries messages among the modules assigned to that vehicle network. The control module monitors bus K communication; this code sets when bus K is off, often because repeated errors place a CAN controller in a bus-off state.

Common causes

Most likely first.

1. CAN controller in bus-off state
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 all codes and freeze-frame data, then identify which bus K modules are unresponsive and whether a CAN controller reports bus-off or repeated communication errors.
2. Inspect bus K wiring, connectors, and grounds for breaks, corrosion, loose pins, and shorts that could cause the errors.
3. Check gateway status for bus K routing faults or isolation and compare this with which modules no longer communicate.
4. With power removed as specified by the manufacturer, test bus K wiring for continuity and shorts and check termination against the manufacturer's specification.
5. If wiring and termination pass, isolate bus K modules under the manufacturer's diagnostic procedure to identify a controller or gateway disrupting the network.

Common fixes

• Repair broken, damaged, or shorted bus K wiring.
• Clean or repair corroded and loose bus K connectors.
• Replace a terminating resistor if it is outside the manufacturer's specification.
• Repair or replace the gateway if it routes or isolates bus K incorrectly.
• Repair or replace a module confirmed to be forcing bus K offline.

Can I keep driving?

Bus K being off can put affected systems into limp mode or make functions unavailable, so avoid demanding driving and do not depend on those functions. Stop if essential or safety-related operation is affected; continued driving may compound the loss of module communication.