P24EF: Control Module Wake-up Circuit/Open
The wake-up line that brings a sleeping ECU back from low-power mode is open. Many networks use a dedicated hardware wake-up wire (door-latch trigger, terminal 15, CAN wake-up) so modules can stay asleep with the ignition off. Without it, the module either fails to wake up at start-up or stays awake and drains the battery.
What P24EF means
P24EF is a generic OBD-II powertrain code in the computer & electrical group. In plain English: the computer found an electrical fault in that circuit: an open, short or bad connection, or a failed component.
- Check engine light
- Usually on
- Emissions-related
- No
- Limp mode possible
- Not typical
- Drive cycle to clear
- Not required
Get it fixed
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Common causes
- 01Broken wake-up wire or unplugged connectorMost likely
- 02Failed wake-up input stage in the modulePossible
- 03Pin pushed back out of connector bodyLess likely
Can I drive with P24EF?
Usually yes, for a short time.
The car will often drive normally, but get it diagnosed soon. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
Why we rate it moderate
- Turns on the check engine light
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose P24EF
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P24EF. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Fix other faults first
If other codes are stored, start with power-supply, sensor-circuit and communication codes. They can cause this code as a side effect.
- 3
Test the circuit
Inspect the wiring and connector at the wake up circuit and control module for damage, corrosion or chafing. With a multimeter, check supply voltage, ground and signal against the specifications in the service manual for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Broken wake-up wire or unplugged connector; failed wake-up input stage in the module; pin pushed back out of connector body. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and drive the car under the conditions in the freeze-frame data to confirm it does not return.
P24EF repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Moderate
- Good DIY job?
- Usually a shop job
Needs a scan tool and some experience with testing.
Parts and systems involved
- Wake up circuit
- Control module
- Wiring harness
P24EF FAQ
What does P24EF mean?
P24EF means “Control Module Wake-up Circuit/Open”. The wake-up line that brings a sleeping ECU back from low-power mode is open. Many networks use a dedicated hardware wake-up wire (door-latch trigger, terminal 15, CAN wake-up) so modules can stay asleep with the ignition off. Without it, the module either fails to wake up at start-up or stays awake and drains the battery.
Is P24EF serious? Can I keep driving?
We rate P24EF as moderate severity. Usually yes, for a short time. The car will often drive normally, but get it diagnosed soon. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
What causes P24EF?
The most common causes, from most to least likely: Broken wake-up wire or unplugged connector; Failed wake-up input stage in the module; Pin pushed back out of connector body. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P24EF?
Typical labor is about $65–$250 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix P24EF myself?
DIY difficulty is moderate. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will P24EF clear itself?
If the fault was intermittent, the warning may go off once the computer stops seeing it, but the code stays in memory. Fix the cause; clearing the code alone doesn’t repair anything.