U0259: Lost Communication With Special Purpose Vehicle Control Module A

What it means

A control module has stopped receiving expected messages from special purpose vehicle control module A. The code identifies the communication loss; upfitted functions controlled by that module may be affected.

How it works

Special purpose vehicle control module A manages functions installed for a particular vehicle use or upfit and exchanges status over the vehicle network. This code sets when a monitoring module no longer receives the expected messages from module A.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

Symptoms

• Functions controlled by the special purpose module may be unavailable
• A communication fault may be stored

How to diagnose it

1. Save freeze-frame data and scan all modules for communication faults to determine whether module A alone is offline or the network has a broader problem.
2. Identify which upfitted functions are unavailable and confirm whether this vehicle assigns them to special purpose vehicle control module A.
3. Inspect module A's connectors and related bus wiring for loose plugs, corrosion, damage, or signs of an open or short.
4. Check module A's power and ground against the manufacturer's procedure, since an unpowered module cannot send network messages.
5. If its supplies are correct, test the network wiring at module A for opens or shorts using the manufacturer's procedure.

Common fixes

• Reconnect or secure a loose connector at special purpose vehicle control module A.
• Repair damaged or corroded bus wiring or connector terminals serving module A.
• Restore a missing power or ground connection to module A.
• Replace module A if its wiring and supplies pass checks but communication does not return.

Can I keep driving?

The effect depends on the upfitted functions controlled by module A, so avoid using any affected equipment until its operation is confirmed. If the fault affects equipment needed for safe vehicle operation, do not drive until that function is restored.