U0420 Code: Invalid Data Received From Power Steering Control Module
The electric power steering module is talking, but its steering angle or torque data doesn't add up.
At a glance
Severity: Moderate
- Meaning
- Invalid Data Received From Power Steering Control Module
- System
- Module Communication · Network
- Safe to drive?
- With caution
- Typical repair cost
- $30–$2,800
- DIY difficulty
- Moderate
U0420 is logged when a module such as the PCM, ABS/stability, lane-keeping camera or park-assist module receives data from the power steering control module that fails a range or consistency check. On cars with electric power steering (EPS), the steering module shares steering angle, driver torque and assist status; stability control, lane-keep assist and automatic parking all depend on it. The usual reasons are a steering angle or torque sensor that lost its calibration after an alignment, rack or column replacement or battery disconnect, EPS software that doesn't match the other modules, or voltage sagging when the EPS motor draws heavy current at low speed. The EPS module's own fault memory usually tells you which one it is.
Can I keep driving? Steering assist usually still works, but it may become heavy without warning, especially at parking speeds, and driver-assist features will be off. Drive carefully and avoid tight maneuvering until the cause is found; if steering becomes heavy, stop and have it checked.
How to read U0420
- U Network
- 0 Generic (SAE)
- 4 Module Communication
- 20 Specific fault
Symptoms
- Power steering warning light (steering wheel symbol) on
- Steering goes heavy intermittently, most noticeable when parking
- Lane-keep assist, lane-centering or automatic parking unavailable
- Stability or traction control light on at the same time
- Steering wheel not centered or assist uneven left versus right
- Warnings appear after battery replacement, alignment or steering repairs
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Steering angle or torque sensor not calibrated after alignment, rack/column replacement or battery disconnect
- Voltage dropping under the EPS motor's load: weak battery, poor ground or charging problem
- EPS module software outdated or mismatched with other modules
- Replacement or used steering rack/column module not configured for the vehicle
- Loose or corroded EPS power, ground or signal connector
- Internal fault in the EPS module or its torque sensor
Diagnosis step by step
Read the power steering module
Scan all modules and open the power steering module directly. Sensor calibration, supply voltage or motor codes stored there are the real fault; U0420 in other modules is the echo.
Tools: OBD-II scanner
Measure voltage at the EPS under load
EPS motors can draw very high current at full lock. With the engine running, measure voltage at the EPS power feed while turning the wheel lock to lock at a standstill; it should stay above roughly 12.5 V. A deeper drop means a battery, cable or ground problem.
Tools: Multimeter
Check the EPS ground and main feed
Clean and tighten the heavy EPS ground and main fuse connections. A voltage-drop test across the ground under load should show less than about 0.2 V.
Tools: Multimeter, Screwdriver
Check steering angle and torque data
With wheels straight, steering angle should read near 0 degrees and driver torque near 0 Nm with hands off. If the angle is offset or torque doesn't return to zero, the sensor needs calibration or replacement.
Tools: OBD-II scanner
Run steering calibration and end-stop learn
Use a scan tool that can run the EPS steering angle zero-point and end-stop learn routines, and recalibrate the stability control steering sensor afterward if the vehicle has a separate one.
Tools: OBD-II scanner
Check software and configuration
If the rack or column was replaced, confirm the module was programmed for this vehicle. Ask a dealer whether newer EPS software exists; many U0420 complaints are cured by a reflash.
Tools: OBD-II scanner
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Steering angle / EPS calibration | No | $80–$200 |
| Replace battery or repair EPS ground | Yes | $30–$300 |
| EPS software update at a dealer | No | $100–$300 |
| Configure replacement steering rack/column module | No | $120–$300 |
| Replace EPS column or rack assembly | No | $900–$2,800 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Field data
| Chevrolet | 10 | Colorado, Ss | |
|---|---|---|---|
| Ford | 5 | Explorer, Flex, Fusion Energi | |
| Chrysler | 2 | 200 | |
| GMC | 2 | Canyon | |
| Jeep | 2 | Cherokee, Compass |
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Depends
U0420 on its own doesn't normally fail the emissions test. Vehicles in states with a safety inspection may be rejected if the power steering or stability warning stays lit.
Frequently asked questions
Will I lose power steering with U0420?
Usually not completely. Assist may be reduced or go heavy intermittently, especially at low speed. If the steering suddenly becomes heavy and stays that way, the EPS has shut down and the car should be checked before further driving.
Why does this code show up after an alignment?
Adjusting the tie rods changes where 'straight ahead' is. If the steering angle sensor isn't recalibrated afterward, the EPS reports an angle that doesn't match the car's actual direction.
How is U0420 different from U0131?
U0131 means the power steering module has stopped communicating. U0420 means it still communicates but sends values that fail plausibility checks, which usually points to calibration, voltage or software.
Can a battery problem really cause steering codes?
Yes. Electric power steering is one of the biggest electrical loads in the car. A weak battery or bad ground lets voltage collapse at full lock, and the module then flags its own data as unreliable.
Sources
- SAE J2012 – Diagnostic Trouble Code Definitions
- ISO 15031-6 – Road vehicles, diagnostic trouble code definitions (EOBD)
- Manufacturer public service information (cross-checked)
- NHTSA Complaints API
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