Network, generic

U024A Lost Communication With Interior Lighting Control Module A

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Interior lighting control module A switches and dims cabin lights such as dome, footwell and ambient strips. In newer cars these are often small LIN nodes under a master, usually the body controller. A Microchip demo board for LIN ambient light illustrates the traffic: the master sends colour and brightness per zone and polls a status frame back. GM's Saab 9-5 documentation states that on a LIN subsystem the primary module records a lost-contact code for any node that stops answering, and that is the route by which U024A is normally stored. No manufacturer documents U024A publicly, so timeouts are unknown. Typical findings are a loose plug at a roof or door light unit or a LIN line chafed in the headliner. Cabin lights stay dark or on, and ambient colours freeze. Module B is U02BF; corrupt data from A give U054B.

Likely causes

Loose or corroded plug at a roof, door or footwell light unit
LIN line chafed or pinched in headliner, door or trim
Lighting module without power or ground
Lighting module internally faulty

Symptoms

  • Interior lights do not come on or stay on
  • Ambient lighting colour or brightness cannot be changed

Repair estimate

DifficultyEasyDIY possible
Parts and labour€0–400
Time0.3–2 h

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

Parts involved

interior lighting module acan bus

Related codes

U02BFU054BU05C0

References: http:, saabwisonline.com, en.wikipedia.org.