U0420Generic code

U0420 Code: Invalid Data Received From Power Steering Control Module

The U0420 code means the power steering module is sending messages, but with data that does not make sense or is out of range. Steering assist may be affected as a result. The module is often just passing along a bad reading from one of its own sensors.

Severity
Medium
Can I keep driving?
Yes, but with caution
Estimated cost
$0 to $1,200
Difficulty
Hard
System
Communication Network
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the U0420 code means

Unlike a loss of communication, here the messages from the power steering module do arrive, but their content is not valid: impossible values, counters that do not advance or incompatible data. The module that receives that data stores the U0420 code and stops using it.

The usual causes are a sensor connected to the power steering module that gives wrong readings (the module forwards the bad data), incompatible software after a module was replaced or reprogrammed, an incorrect configuration, or an internal failure. Check the codes stored in the power steering module itself first: they usually point to the origin.

After a module is replaced, it often has to be configured (coded) so that it sends data in the format the other modules expect. Skipping that step is a common reason the code appears right after a repair.

A typical example: a damaged ABS wheel speed sensor makes the ABS module send a wrong speed, and the transmission or the cluster store invalid data from that module. That is why repairing the original sensor often clears the invalid data codes in the other modules without touching anything else.

U0420 code symptoms

  • Warning lights on.
  • Steering assist may be affected.
  • Codes stored in the sending module.

Likely causes of the U0420 code

  1. Codes stored in the power steering module itself. One of its sensors is giving wrong readings.
  2. Incompatible software or configuration. This follows a module that was replaced or reprogrammed.
  3. Unstable supply voltage. Modules send wrong data when they reset.
  4. Internal failure of the power steering module. Only after sensors, software and power have been ruled out.

How to diagnose the U0420 code step by step

  1. Read the codes in the power steering module and solve those first.
  2. Check for recent replacements or reprogramming.
  3. Verify the module configuration with a compatible scan tool.
  4. Measure the battery voltage.

How to fix the U0420 code

  • Resolve the codes in the sending module.
  • Configure or update the module software.
  • Replace the module if it has an internal failure.
  • Clear the codes in all modules.

Technical reference data

  • Invalid data includes out-of-range values, message counters and incorrect checksums.
  • These are reference values: check the manufacturer data for your vehicle.

Brand-specific notes

After the repair, clear the codes in every module and confirm the U0420 code stays gone. Many modules keep old U codes from when the fault was present. Accessories installed later (alarms, GPS trackers, OBD2 adapters left plugged in permanently) are a frequent cause of network problems.

Frequently asked questions about U0420

What does the U0420 code mean?
It means the power steering module is sending data that another module considers invalid, such as impossible values or counters that do not advance. The receiving module stored the code and stopped using that data.
Can I drive with a U0420 code?
With caution, depending on the system affected. Steering assist may be reduced, so the wheel can feel heavy, especially at parking speeds. Have it checked soon.
Is the power steering module bad?
Not necessarily. Often it is only forwarding a wrong reading from one of its sensors, so read its own codes before you replace anything.
What is coding?
It is the configuration that adapts a module to the equipment on the vehicle. A replacement module often needs it before it sends data in the expected format.
How much does it cost to fix U0420?
Between $0 and $1,200. Clearing a sensor fault or recoding can be cheap, while replacing and programming a module is at the top of the range.
Will a U0420 code clear itself?
Only if the cause was temporary, such as a voltage dip. If the bad data is still being sent, the code will return after you clear it.
What is the most common cause of U0420?
A faulty sensor on the power steering module, or software and configuration that do not match after a module was replaced or reprogrammed.

Related codes

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