U025F: Lost Communication With Electronic Brake Booster Control Module B

What it means

A control module has stopped receiving expected messages from electronic brake booster control module B. Brake-assist behavior may be affected; the code alone does not establish the resulting braking 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

Electronic brake booster control module B exchanges status and assistance-control messages with other modules over the vehicle network. The receiving module sets U025F when it does not receive the expected messages from that specific booster module; the code alone does not identify the braking mode or prove the booster itself has failed.

Common causes

Most likely first.

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

Symptoms

• A brake-system warning may appear
• Brake assist or related functions may be limited

How to diagnose it

1. Record all-module codes and freeze-frame details, then check whether U025F is current and whether other network or low-voltage faults appeared at the same time.
2. Use a scan tool to see whether electronic brake booster control module B responds and whether related brake-system modules report the same communication loss.
3. Inspect the named module's connectors and accessible bus wiring for looseness, corrosion, water entry, chafing, or damage.
4. Check the module's power and ground circuits under the conditions specified by the manufacturer, since loss of either can make it disappear from the network.
5. If power, ground, and wiring pass, test the network circuit to module B for an open or short using the manufacturer's procedure before considering module replacement.

Common fixes

• Restore a loose or corroded connector at brake booster control module B.
• Repair damaged bus wiring to module B.
• Restore the module's power or ground supply if testing identifies a fault.
• Replace and configure module B only after its circuits and network connection test correctly.

Can I keep driving?

Treat any brake warning, changed pedal feel, or reduced assistance as urgent; avoid driving and arrange safe recovery if braking feels abnormal. Even without an obvious change, drive cautiously only as needed to reach a safe place because assistance or related brake functions may be limited.