What it means
The control module wake-up circuit is open or has an electrical fault. The code does not establish whether the affected module will fail to wake or remain awake.
At a glance
- Usually lights the check-engine light
How it works
A wake-up circuit signals a control module when it should become active. The module or monitoring controller checks whether that circuit has an electrical path. P24EF sets when the wake-up circuit is detected as open or otherwise electrically interrupted; it does not by itself show whether the module failed to wake or stayed awake.
Common causes
Most likely first.
- Broken wake-up wire or unplugged connector
- Failed wake-up input stage in the module
- Pin pushed back out of connector body
Symptoms
- Check-engine light
- A control module may fail to wake or communicate
- Intermittent electrical functions
How to diagnose it
- Scan all modules and note which ones fail to communicate or show intermittent communication, then record freeze-frame and related network codes.
- Check the affected module's connectors and the wake-up wire for disconnection, damage, corrosion, or pinched sections.
- Inspect connector terminals for a pushed-back pin or poor terminal fit, paying particular attention to the wake-up circuit pins.
- Use the wiring diagram to identify the wake-up circuit endpoints, then check continuity with power isolated as specified by the manufacturer.
- Check for an open between the controlling switch or module and the affected module, separating connector and harness sections to locate the break.
- If wiring and terminals test correctly, follow the manufacturer's procedure to test the module's wake-up input stage.
Common fixes
- Reconnect a loose module connector or restore a pushed-back terminal to its proper position.
- Repair a broken or chafed wake-up wire.
- Clean or replace corroded terminals and restore a secure connector fit.
- Replace the control module only if its wake-up input fails the manufacturer's tests.
Can I keep driving?
Driving may be unsafe if the affected module controls essential functions or if warning lights or electrical features behave unpredictably. Avoid relying on functions that are intermittent and arrange diagnosis before an important trip.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.