What U0420 means
The Power Steering Control Module is present on the data bus but the values it reports are implausible — out of range, frozen, or failing the checksum or rolling-count check.
How the engine computer detects it
The receiving modules reject the data. Power-steering assist may be reduced or disabled. Causes include a faulty sensor feeding the module, internal computation errors, a software or calibration mismatch after a repair, or bus interference corrupting the frames.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Common causes
- EPS module internal fault Possible
- CAN corruption causing checksum errors Possible
- Gateway module routing CAN messages incorrectly Less likely
How to diagnose U0420
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: power steering module, can bus wiring.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report U0420 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Chevrolet Colorado | 2015–2016 | 10 | 50k | |
| Ford Fusion | 2014–2016 | 3 | — | |
| Jeep Cherokee | 2015–2020 | 3 | — |
Counts of owner complaints to the NHTSA that mention U0420 (30 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- U
- Network
- 0
- Generic (SAE) code
- 420
- Specific fault
Questions drivers ask
Can I drive with code U0420?
Carefully, and only if the steering feels normal. Power steering assist may be reduced or switched off, which makes the wheel heavy. If steering is heavy or unpredictable, don't drive the car.
Often reported together
Codes that owners mention in the same NHTSA complaints as U0420. They can point to a shared cause, so it's worth checking them together.
- C0545VIN Not Programmed or Incompatible - BSCM7 complaints
- C0051Power Steering Position Sensor Performance4 complaints
- U0131Lost Communication with Power Steering Control Module4 complaints
- U0415Invalid Data Received from ABS Control Module4 complaints
- U0121Lost Communication with ABS Control Module3 complaints
- U0140Lost Communication with Body Control Module3 complaints
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.