U015B: Lost Communication With Power Steering Control Module B

What it means

ECU lost CAN communication with power steering control module B. Steering assist may be reduced. A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp 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

Power Steering Control Module B manages or supports a power steering function and shares steering-related information over the vehicle network. U015B sets when the reporting module stops receiving expected messages from this specific steering module for the required time, which can reduce or disable steering assist.

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. Scan all modules for U015B and related communication codes, and review freeze-frame data for low voltage or a wider network interruption.
2. Check battery condition and charging-system operation, as low voltage can interrupt the steering module's communication or operation.
3. Inspect Power Steering Control Module B's power and ground supplies, fuses, network connector, and wiring for damage or corrosion.
4. Use a scan tool to check whether module B responds, and assess steering effort with the vehicle safely stationary.
5. If its supplies are correct, test the CAN wiring and gateway path for opens, shorts, or routing faults.
6. If the network is intact, investigate the module and any network termination fault according to the manufacturer's specification.

Common fixes

• Restore battery charge or repair a charging-system fault.
• Repair a blown fuse or poor power or ground connection to Power Steering Control Module B.
• Repair damaged CAN wiring or connector terminals, or correct a verified gateway routing fault.
• Repair a confirmed network termination problem to the manufacturer's specification.
• Repair or replace Power Steering Control Module B if its supplies and network path are sound.

Can I keep driving?

If steering assist is reduced or steering effort changes, stop in a safe place and avoid continuing in traffic; steering may require much more effort. Have the fault checked before relying on the vehicle, especially if steering feels unpredictable.