Network, generic

U0420 Invalid Data Received From Power Steering Control Module A

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Low battery voltage during cranking corrupts steering module start-up data
Steering module or receiving module software needs an update
Corroded connector or poor ground at the steering module

Symptoms

  • 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

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€50–600
Time0.3–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

power steering modulecan bus wiring

Related codes

U0131U0320U0428U0415U045C

References: gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.