OBD-II trouble code
U0420: Invalid Data Received From Power Steering Control Module A
A module is receiving messages from the power steering control module, but the data is implausible or out of range. Electric power steering may reduce or suspend assist as a precaution — the wheel gets heavy but the car still steers. The connection is alive; the content is wrong.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $1,500
- DIY difficulty
- Shop recommended
What does U0420 mean?
Vehicles with electric power steering (EPS) use a power steering control module to read steering torque and angle, drive the assist motor, and share steering data with the stability control system over the network. U0420 sets when a receiving module is still hearing from the power steering control module, but the data inside its messages is invalid — a reported torque, angle, or assist value that's out of range, implausible, or in conflict with what other modules observe. That distinguishes it from U0131, the lost-communication version, where the module goes silent altogether. The 'A' identifies the primary steering module on vehicles that may network more than one.
The system's response is protective. Steering assist that acts on bad data could tug the wheel when it shouldn't, so EPS systems respond to untrusted values by reducing assist, disabling it entirely, or reverting to a default assist map — and stability control features that depend on steering angle may switch themselves off at the same time. The steering never disconnects: the mechanical linkage between the wheel and the tires remains, so the car steers with heavier effort, most noticeable at parking speeds.
Causes follow the invalid-data pattern with a few steering-specific standouts. An uncalibrated or drifting steering angle sensor is the leading trigger — especially after an alignment, steering or suspension repair, or battery disconnect on vehicles that require a sensor relearn. Low system voltage is another classic, since the assist motor is one of the largest electrical loads on the car. Degraded torque sensors, corrupted or mismatched module software, and wiring or connector damage round out the list. Companion codes — steering angle sensor codes or a C-series EPS code — usually name the specific fault.
Common causes
- Steering angle sensor out of calibration after alignment, steering/suspension work, or battery disconnect
- Failing steering torque or angle sensor producing implausible values
- Low system voltage or a weak battery/charging system under the EPS motor's heavy load
- Outdated, corrupted, or mismatched power steering module software
- Power steering module or steering column/rack replaced without required programming or calibration
- Damaged wiring or connectors in the EPS circuit or network bus
- Power steering control module internal fault
Symptoms
- Power steering warning light or EPS message on the display
- Noticeably heavier steering effort, especially at parking speeds
- Assist cutting out intermittently or varying unpredictably
- Stability control or lane-keeping features disabled (they rely on steering angle data)
- Companion steering angle sensor or C-series EPS codes stored alongside U0420
- Vehicle still fully steerable — the mechanical connection is never lost
Diagnostic steps
- 1.Read ALL stored codes — a steering angle sensor code or EPS-specific C-code usually names the underlying fault.
- 2.Ask about recent work: alignments, steering or suspension repairs, and battery disconnects commonly leave the steering angle sensor needing a relearn.
- 3.Check battery and charging system voltage; the EPS motor's load makes this system especially sensitive to weak voltage.
- 4.Compare reported steering angle against actual wheel position in live data — an offset or drifting value confirms a calibration or sensor fault.
- 5.Perform the manufacturer's steering angle sensor calibration/relearn procedure and retest before replacing hardware.
- 6.If data remains implausible after calibration with healthy voltage and wiring, test the torque sensor and module per the service procedure; many EPS designs are serviced as a column or rack assembly.
Repair cost
$100 – $1,500
A steering angle sensor relearn/calibration runs $100-$200 and resolves many cases, especially after alignments or battery work. Software updates run $100-$300, and a standalone steering angle sensor $150-$500 installed. The expensive outcome is EPS hardware: on many vehicles the torque sensor and module are integrated into the steering column or rack, and an assembly replacement with programming can run $800-$1,500. Diagnose thoroughly before going there.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with module communication / can bus diagnosis preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.