Network, generic

U04BA Invalid Data Received From Switch Input Module A

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

A switch input module collects the positions of several buttons and reports them to other control units as network frames. U04BA means that frames from module A keep arriving, but the receiver, usually the body controller, rejects their content: a switch state outside the defined values, a wrong message counter, a failed checksum or an unexpected length. An Eaton patent describes such a module in which a controller polls each switch address and acts only on replies carrying a valid address and state. Which buttons belong to module A is up to the carmaker; no maker documents this code publicly. If module A falls silent, U01B7 is set instead. For the driver, the buttons handled by this module may do nothing or trigger the wrong function.

Likely causes

Switch module or receiving controller with incompatible software or coding after repair
Switch input module A internally faulty (moisture, damaged switch contacts)
Corroded connector or chafed data lead corrupting the frames

Symptoms

  • Buttons served by the module inoperative or acting intermittently
  • Code stored in the body controller without a warning lamp

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€0–350
Time0.5–2 h

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

Parts involved

switch input module a

Related codes

U01B7U04BBU04BC

References: patents.google.com, saabwisonline.com.