P024B: Charge Air Cooler Bypass Control A Stuck

The charge air cooler bypass is a flap or valve that routes compressed air around the charge air cooler, so the engine and exhaust warm up faster after a cold start; when warm it closes or opens partly to control intake air temperature. It is driven by an electric motor with a built-in position sensor or by a solenoid and vacuum can. P024B means the bypass flap does not move at all despite being commanded – the position signal stands still or the air temperature shows no reaction. Bosch's patent describes exactly the case of a valve stuck closed or a blocked bypass, which raises emissions during warm-up. Stuck open, the charge air gets hotter and power drops; stuck closed, warm-up takes longer. No manufacturer document using this code was found – GM and Ford do not use the bypass codes; the description rests on CARB's component monitoring requirement and a Bosch patent on the bypass valve.

Symptoms

• Check engine light on
• Stuck open: higher charge air temperature, loss of power
• Stuck closed: longer warm-up

Most likely causes

• Flap seized or coked
• Actuator faulty (gear, motor)
• Vacuum supply missing (pneumatic type)
• Position sensor reading constant

What to check, in order

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

1. Check the hoses, clamps, and intercooler
2. Use the scanner to command the movement and compare the actual position with the requested one.
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 affects emissions.

What each character of P024B means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 2: Fuel injection
• 4B: Specific fault in that system

Frequently asked questions

Can I keep driving with code P024B?

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 P024B?

The most common causes are: flap seized or coked; actuator faulty (gear, motor); vacuum supply missing (pneumatic type).

Related codes

• P024ACharge Air Cooler Bypass Control A Range/Performance
• P024DCharge Air Cooler Bypass Position Sensor A Circuit Range/Performance
• P022ACharge Air Cooler Bypass Control A Circuit/Open
• P026ACharge Air Cooler Efficiency Below Threshold
• P0299Turbocharger/Supercharger A Underboost Condition

Sources

• law.cornell.edu: 13 CCR 1968.2
• patents.google.com: US8417484

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.