P25EC: Supercharger Disconnect Clutch Circuit Low

The engine module measures a voltage on the supercharger clutch control line that is lower than expected for the commanded state. Most often the line has a short to ground. What that does depends on how the coil is switched: with a ground-side driver a grounded control wire can leave the coil permanently energised, so the blower keeps turning; with a supply-side driver the clutch simply stays off and the low-speed boost is gone. Neither the threshold nor a detection time has been published for this code, and no manufacturer documents it publicly; CARB requires output circuits to be checked for such faults. P25ED is the high-side counterpart, P25EB the plausibility fault. The control module usually disables clutch control.

Symptoms

• Check engine lamp on
• Supercharger permanently engaged or permanently off, depending on circuit design
• Reduced power at low engine speed

Most likely causes

• Control wire shorted to ground, often chafed on brackets or the engine block
• Clutch coil shorted internally
• Faulty output stage in the engine control module

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the hoses, clamps, and intercooler
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Compare commanded and actual pressure in live data
4. Check the actuator's movement
5. Check the vacuum hoses and the solenoid valve
6. Check the oil and the turbo shaft play before replacing it

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P25EC means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 5: Speed and idle
• EC: Specific fault in that system

Frequently asked questions

Can I keep driving with code P25EC?

Drive without demanding power and go to a repair shop soon. If you see a lot of blue smoke or hear a metallic noise, shut off the engine.

What causes code P25EC?

The most common causes are: control wire shorted to ground, often chafed on brackets or the engine block; clutch coil shorted internally; faulty output stage in the engine control module.

Related codes

• P25EBSupercharger Disconnect Clutch Circuit Range/Performance
• P25EDSupercharger Disconnect Clutch Circuit High
• P25FESupercharger Disconnect Clutch
• P25EASupercharger Disconnect Clutch Stuck Closed

Sources

• law.cornell.edu: 13 CCR 1968.2
• mobilityengineeringtech.com: 42215 sae ma 01421
• en.wikipedia.org: Twincharger

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.