CAN network

U0420 — Invalid Data Received from Power Steering Control Module

Severity: medium Drive with care, to a shop

What U0420 means

A control module on the network received implausible data from the power steering module, such as steering angle or torque values. The steering module normally broadcasts this data continuously to other modules (ESC, instrument cluster, engine control), which compare it with their own sensor readings. When the values are out of range or do not agree, U0420 is stored.

Symptoms

  • Steering warning light on
  • ESC (stability control) disabled
  • Several warning lamps lit at once
  • Reduced or lost power steering assist
  • Functions of the affected module unavailable

Possible causes

  1. Faulty steering angle or torque sensor
  2. Steering rack actuator problem
  3. Lost calibration in the steering module
  4. CAN bus wiring fault: open, short or chafed harness
  5. Faulty control module disrupting the bus
  6. Corroded connectors or terminals
  7. Power supply or ground fault at a module

How to diagnose

  1. Run a full-system scan and map which modules are missing or reporting faults
  2. Review freeze frame data and whether the code is current or intermittent
  3. Check battery voltage and charging output, since low voltage causes false network codes
  4. Measure CAN bus voltages and resistance at the diagnostic connector (typically about 60 ohms between CAN-H and CAN-L)
  5. Inspect wiring and connectors at the steering module and steering angle sensor for moisture, corrosion or chafing
  6. Check power and ground supply to the affected module
  7. Compare live steering angle data with the actual wheel position
  8. Disconnect suspect modules one at a time, only following a documented factory procedure

Common fixes

  • Repair damaged CAN bus wiring and clean or replace corroded connectors
  • Fix the power or ground fault at the module
  • Recalibrate or reprogram the steering module and steering angle sensor
  • Replace the faulty sensor or the electric power steering rack
  • Replace a faulty module that is loading the bus and code it to the vehicle

Questions and answers

What does U0420 mean?

It is a communication fault: another module received data from the power steering module that fails plausibility checks. The cause can be the module itself, a sensor or the CAN bus.

Can I drive with U0420?

Only carefully and for a short distance to get it diagnosed. You may lose power assist and stability control, which reduces safety.

Can I just clear U0420?

Clearing it may work briefly, but if the cause is wiring, power or a sensor, the code will return. Find the root cause 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.