U01A3: Lost Communication With Hybrid/EV Battery Interface Control Module D

What it means

Communication with Hybrid/EV Battery Interface Control Module D was not received as expected. This code does not identify the cause or specify the communication network used.

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

Hybrid/EV Battery Interface Control Module D is a separate controller that exchanges information about the battery system with other modules. U01A3 sets when expected messages from interface module D are missing; it does not mean that modules A, B, or C are also at fault.

Common causes

Most likely first.

1. Module unpowered
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. Save freeze-frame data and scan all modules to see whether interface module D alone has lost communication or multiple battery controllers are offline.
2. Check for high-voltage or battery warnings, reduced-power operation, disabled functions, or failure to enter ready mode.
3. Inspect accessible low-voltage connectors and wiring for interface module D for damage, corrosion, water intrusion, or poor connection.
4. Check the module's relevant low-voltage fuse, power, and ground circuits using the manufacturer's procedure.
5. Have a qualified technician investigate gateway routing and network wiring; high-voltage interlock checks must follow the manufacturer's safety procedure.

Common fixes

• Repair damaged or corroded accessible low-voltage wiring or connector terminals for interface module D.
• Restore module D's power or ground supply and address the reason for any blown fuse.
• Correct a gateway routing or configuration fault affecting module D.
• Repair a confirmed network or interlock fault according to the manufacturer's procedure.

Can I keep driving?

If a high-voltage warning, loss of propulsion, or abnormal battery behavior occurs, stop safely and do not continue driving. Otherwise, arrange prompt diagnosis because battery functions may be limited, and do not access high-voltage components.