U0420 code meaning
Invalid Data Received From Power Steering Control Module A
What U0420 means
U0420 is stored when a listener gets frames from power steering control module A, the electric assist unit on rack or column, yet judges their content unusable. GM's 2025 tables name several listeners: the ECM tests the steering wheel information for bad counter, protection value or checksum and needs 8 failures within 18 samples for a Type C fault with no MIL; the EBCM runs similar Type C tests, and the EOCM3 assistance controller checks torque overlay and assist status (3 of 4 or 6 of 10 frames) and switches adaptive cruise off. Mazda bulletin 15-003/20 blames U0420:68 in the front camera on low voltage during cranking, which spoils the EPS centre learning; new EPS software helps. Jeep 08-094-25 (2025 Wagoneer) reflashes the EPS when U0420-00 comes with a MIL. U0131 is lost contact, U0320 software.
U0420 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor0.3 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0420
- Adaptive cruise, lane keeping or emergency braking unavailable
- Stability control or steering warning in the cluster
- Code returns after cold starts with a weak battery
Common causes of U0420
- Most likelyLow battery voltage during cranking corrupts steering module start-up data
- PossibleSteering module or receiving module software needs an update
- Less likelyCorroded connector or poor ground at the steering module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Power steering moduleCAN bus wiring
What each part of U0420 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 20 | The exact fault in that area. |
What to do next
- Note U0420 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0420
What does U0420 mean?
U0420 means "Invalid Data Received From Power Steering Control Module A". U0420 is stored when a listener gets frames from power steering control module A, the electric assist unit on rack or column, yet judges their content unusable. It is a generic code, so it means the same on every make.
Is it safe to drive with U0420?
U0420 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0420 fail an emissions test?
U0420 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U0420 to fix?
Difficulty: workshop only. A typical repair takes 0.3 to 2 hours of work. This is a job for a workshop.
Will U0420 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.