U025A: Lost Communication With Special Purpose Vehicle Control Module B

What it means

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

How it works

Special purpose vehicle control module B manages its assigned upfitted functions and reports status to other modules over the vehicle network. U025A sets when a monitoring module stops receiving the expected messages specifically from module B.

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. Record freeze-frame data and scan the vehicle for other communication codes to check whether module B is the only module missing from the network.
2. Check which upfitted functions are unavailable and verify whether they are assigned to special purpose vehicle control module B.
3. Inspect module B's connectors and associated bus wiring for looseness, corrosion, physical damage, or a possible open or short.
4. Verify module B's power and ground connections using the manufacturer's procedure before treating the module as failed.
5. If power and ground are good, test the network circuits to module B for opens or shorts according to the manufacturer's procedure.

Common fixes

• Secure a loose connector at special purpose vehicle control module B.
• Repair damaged bus wiring or corroded terminals connected to module B.
• Restore module B's power or ground if either is missing.
• Replace module B if its supplies and network wiring are sound but it remains offline.

Can I keep driving?

Whether the vehicle can be used depends on the upfitted functions assigned to module B. Avoid operating affected equipment, and do not drive if it performs a function required for safe operation.