CAN network

U0120 — Lost Communication with Electric Power Steering (EPAS) Module

Severity: high Drive with care, to a shop

What U0120 means

U0120 means one or more control units stopped receiving messages from the electric power steering (EPAS) module on the CAN network. This module normally runs the assist motor on the steering rack or column, adjusting effort based on speed and steering torque. When communication is lost, assist is usually reduced or shut off.

Symptoms

  • Heavy steering, especially at low speed
  • Power steering warning light on
  • Stability control (ESC) lights may come on
  • Steering assist that comes and goes
  • Other U-codes stored in several modules
  • Fault appears after startup or during voltage drops

Possible causes

  1. Blown power steering fuse or relay
  2. Low battery voltage or poor terminals
  3. Open, shorted or corroded CAN wiring to the steering rack
  4. Poor connection at the EPAS module connector
  5. Failed EPAS module or assist motor
  6. Bad ground at the module
  7. Another module disrupting the CAN bus

How to diagnose

  1. Scan all modules and note other U-codes and EPAS-specific codes
  2. Test battery and charging voltage and inspect the terminals
  3. Check the power steering fuses and relays
  4. Inspect the module connector for moisture, corrosion and bent pins
  5. Check power and ground at the module connector with a multimeter
  6. Test CAN-H and CAN-L resistance and signal to find an open or short
  7. Inspect the harness near the steering rack for chafing
  8. Clear the code and see if it returns

Common fixes

  • Charge or replace the battery and clean the terminals
  • Replace the fuse or relay after finding why it failed
  • Repair the CAN wiring or connector
  • Restore the module ground
  • Replace or reprogram the EPAS module, or replace the steering rack assembly if required

Questions and answers

What does U0120 mean?

It means communication with the electric power steering module over the CAN bus was lost. Other modules can't see its messages, so steering assist may be disabled.

Is it safe to drive with U0120?

Only carefully and for a short distance. The steering stays mechanically connected, but effort can rise sharply, so get it diagnosed soon.

Can a weak battery cause U0120?

Yes. Voltage drops or loose terminals often cause temporary communication loss and this code. Check the battery and fuses first.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.