Network, generic

U0240 Lost Communication With Entrapment Control Module B

Check engine lightUsually off

EmissionsNot relevant

Drive cycleNot required

Limp modeNo

U0240 flags the second anti-trap unit, entrapment control module B, as missing on the network. Where a vehicle has more than one automatically closing panel, for example a sunroof plus a power sliding door, each may carry its own reversal electronics, and B denotes one of them as assigned by the maker; no manufacturer documents U0240 publicly. The protection itself is defined by FMVSS 118, which limits the squeezing force and requires reversal before a test rod is trapped, and by the reversal logic in anti-pinch modules that compare motor current with a learned profile. GM's lost communication logic still applies: a periodic status message stays away with supply at 9-16 V. Pair with U0239 for module A. Automatic closing may be disabled; no MIL.

Likely causes

Module B without power or ground

Wiring broken in a moving harness (sliding door, roof frame)

Entrapment control module B faulty

Symptoms

Automatic close function of a panel disabled
Panel only moves while the switch is held

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€40–700

Time0.5–3 h

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

Parts involved

entrapment module bcan bus

Related codes

U0239 U053A

References: law.cornell.edu, ww1.microchip.com, saabwisonline.com.