Network, generic (extended)

U301C Control Module Wake-up Circuit A High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U301C is the opposite of U301B: wake-up line A is stuck high, usually shorted to a battery-fed wire or held up by a sender that never releases it. The receiving module then gets a permanent wake request. In Ford's 2019 hybrid OBD summary, a high charge wake-up signal is one of the conditions under which the battery energy control module runs its charge contactor and pack contactor checks, so a line stuck high makes the module behave as if charging were requested. The likely result is a module that never falls asleep and a 12 V battery that is flat after a few days of parking. A transceiver like NXP's TJA1043 also needs a change of level to register a wake, so a permanently high line cannot deliver a fresh wake event either. No manufacturer documents U301C publicly.

Likely causes

Wake-up wire shorted to a battery or ignition feed
Sending module or charger holding the wake output on
Moisture bridging the wake pin to a neighbouring supply pin

Symptoms

  • 12 V battery drained after the vehicle has been parked
  • Module or fan audible or active with the vehicle switched off

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–600
Time0.5–3 h

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

Parts involved

wakeup circuit awakeup wiring

Related codes

U301AU301BU3020U301DU3012

References: fordservicecontent.com, nxp.com, law.cornell.edu.