Network, generic

U042B Invalid Data Received From Chassis Control Module A

Check engine lightUsually off

EmissionsNot relevant

Drive cycleNot required

Limp modePossible

Chassis control module A is a generic name for a controller that coordinates chassis functions, and the job behind the letter varies by brand. GM's documents give one concrete owner: the 2020 ten-speed transmission controller (20OBDG03A) treats the integrated chassis control module (ICCM) as chassis control module A and watches its frame $1F7; an L20 engine controller of 2016 also listens to this module. U042B is set when such frames keep arriving but fail content checks, as opposed to U012A, where they stop. No manufacturer documents U042B publicly, so thresholds and lamp behaviour remain open; GM rates the missing-frame case Type C on the transmission and Type B on the engine. Expect chassis or stability messages and a degraded function; a MIL depends on which controller stores it. U042C is module B.

Likely causes

Software fault in the chassis module or the receiving controller

Low voltage or reset of the chassis module during operation

Chassis control module A faulty

Symptoms

Chassis, stability or suspension warning
Chassis functions such as damping or traction aids limited

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€50–900

Time0.3–2.5 h

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

Parts involved

chassis module a

Related codes

U012A U042C U012B

References: gsi.ext.gm.com, gsi.ext.gm.com.