Network, generic (extended)

U350B Control Module Input Power C Circuit Intermittent/Erratic

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U350B reports that supply C fluctuates: it drops or spikes briefly without staying out of range. Where C feeds a motor stage, as in GM's electric brake booster (motor driver supply, voltage sensor 2), such faults surface at moments of peak current, because a loose contact then loses voltage or opens for an instant. GM itself uses only the Low, High and correlation codes for this feed, and no manufacturer documents U350B publicly. The difference from U3509 lies in the timing: short events rather than a steady low level. Typical findings are a fuse with weak clamping, a loose ring terminal on the ground, chafing near the module or corroded pins; check with a recording meter while the load is operating and look for U3019 as a companion code.

Likely causes

Loose fuse contact or ring terminal in feed C or its ground
Chafed wire near the module
Corroded connector pins

Symptoms

  • Brief loss of assist from the motor-driven function
  • Sporadic warning lamp that clears again

Repair estimate

DifficultyMediumDIY possible
Parts and labour€10–500
Time0.5–3 h

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

Parts involved

module power cpower wiring

Related codes

U3508U3509U350AU3507U3019

References: law.cornell.edu, gsi.ext.gm.com.