OBD Control Module Wake-up Circuit/Open
What it means
P24EF stands for Control Module Wake-up Circuit/Open. P24EF is a P code, so the fault sits in the engine, transmission and emissions systems. For P24EF, the second digit places it in auxiliary emission controls. For P24EF, work through the cause list below, cheapest checks first.
Where it lives
For P24EF, the module sits on the circuit this code reports. The description of P24EF reports the module as open.
What to check first
For P24EF, pull the connector and inspect the terminals for spread, corrosion or backed-out pins before testing anything else.
Check these first
- P24EF: Carbon buildup or blockage in the EGR, EVAP, or air injection system
- P24EF: Failed solenoid, valve, or pump in the auxiliary emissions circuit
- P24EF: Wiring, connector, or fuse fault for the emission component
- P24EF: Small leaks in vacuum or EVAP lines
- P24EF: Failing catalytic converter or oxygen sensor reporting incorrectly
What to do next
P24EF belongs to the auxiliary emission controls system. These are the general steps for P24EF, and the exact cause on your vehicle can differ.
- P24EF: Read related codes and freeze frame with an OBD-II scanner
- P24EF: Inspect hoses, valves, and solenoids for leaks, cracks, or carbon buildup
- P24EF: Smoke test the EVAP or intake system if a leak is suspected
- P24EF: Command components on/off with a scan tool and watch them respond
- P24EF: Clean or replace the blocked or failed component
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Updated
Generic SAE J2012 definition. Last updated 2026-08-30.