U0289: Lost Communication With DC/AC Converter Control Module B

What it means

The vehicle bus reports loss of communication with DC/AC inverter module B. Drive-motor torque commands or AC-outlet supply that route through this inverter are unavailable, putting the EV/hybrid drivetrain into a degraded 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

DC/AC converter control module B manages its assigned inverter functions, which may serve drive-motor power conversion or an AC outlet depending on the vehicle. Other hybrid or EV controllers expect messages from module B on the network; this code sets when communication is lost and the functions assigned to B may be unavailable.

Common causes

Most likely first.

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

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. Scan all hybrid or EV controllers for communication, isolation, and low-voltage supply faults, and save freeze-frame data.
2. Check whether converter control module B responds to the scan tool and identify which module B status or functions are missing.
3. Inspect module B's low-voltage connector and harness for looseness, corrosion, damage, or water entry without disturbing high-voltage parts.
4. Test module B's low-voltage power and ground according to the manufacturer's procedure.
5. Have the network branch to module B checked for opens, shorts, or poor connections with the vehicle safely powered down as specified.
6. If its supplies and network circuit are sound, follow the manufacturer's high-voltage diagnostic procedure to determine whether module B itself has failed.

Common fixes

• Reconnect and secure module B's low-voltage connector.
• Repair damaged low-voltage wiring or network connections serving module B.
• Restore module B's low-voltage power or ground.
• Replace module B if the specified checks confirm the module has failed.

Can I keep driving?

Reduced power, a hybrid or EV warning, or limp mode means you should stop when safe and arrange service, because the inverter functions assigned to module B may be unavailable. Do not handle high-voltage components.