Network, generic (extended)

U301E Control Module Wake-up Circuit B/Open

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U301E is the open-circuit code for a second wake-up line, B, on modules that can be roused by more than one source, for example by a door or key event and separately by a charge or timer signal. Ford's patent US5945745A explains why such paths exist at all: a module may sit in a low-current state with the ignition off and still has to answer certain demands, such as panel lighting when the headlamps are switched on. No manufacturer documents U301E publicly; Ford's 2019 hybrid OBD summary shows only the A-side logic of a charge wake-up line. When only line B is open, the module still wakes through A and the bus but ignores the source wired to B, so the fault often shows as one specific function failing to start. If A and B are logged together, check the common sending module or a shared splice first.

Likely causes

Broken wake-up wire B or loose pin
Fault at a splice or sender shared with line A
Source wired to line B not driving its output

Symptoms

  • One wake-dependent function, e.g. timed or remote action, does not start
  • Module otherwise works normally once awake

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 bwakeup wiring

Related codes

U301FU3020U3021U301AU3012

References: law.cornell.edu, patents.google.com, fordservicecontent.com.