U301C code meaning
Control Module Wake-up Circuit A High
What U301C means
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.
U301C at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U301C
- 12 V battery drained after the vehicle has been parked
- Module or fan audible or active with the vehicle switched off
Common causes of U301C
- Most likelyWake-up wire shorted to a battery or ignition feed
- PossibleSending module or charger holding the wake output on
- Less likelyMoisture bridging the wake pin to a neighbouring supply pin
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Wakeup circuit aWakeup wiring
What each part of U301C means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 1C | The exact fault in that area. |
What to do next
- Note U301C and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U301C
What does U301C mean?
U301C means "Control Module Wake-up Circuit A High". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with U301C?
U301C does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U301C fail an emissions test?
U301C is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U301C to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will U301C clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.