What causes fault code P024B?

• Most likely: Mechanical sticking of the bypass flap due to carbon buildup or oil residue • Likely: Faulty bypass valve actuator motor • Possible: Wiring harness damage, open circuit, or short to ground • Rare: Faulty Intake Air Temperature (IAT) sensor providing incorrect reference data

Powertrain (Engine & Gearbox)Standard EOBD

P024B - Charge Air Cooler Bypass Control A Range/Performance

Q: What are the symptoms of fault code P024B?

• Check Engine Light (MIL) illuminated • Reduced engine performance (Limp mode may occur) • Rough idle during cold starts • Increased fuel consumption • Issues with DPF regeneration cycles

Q: How do you fix fault code P024B?

STEP 1: Perform a visual inspection of the wiring harness and connectors for the bypass valve. Check for chafing or corrosion. STEP 2: Manually check the valve's movement (if accessible) to ensure it is not mechanically seized. Clean any carbon buildup. STEP 3: Use a diagnostic scan tool to perform an output test on the actuator. Measure supply voltage (typically 12V during activation) and monitor the PWM control signal. Actuator resistance should typically be between 5-50 Ohms. STEP 4: If the valve is mechanically stuck after cleaning attempt or if the motor is electrically faulty, replace the charge air cooler bypass valve assembly.

Last updated:1 February 2026

Related:Intercooler Bypass Valve, ECU (Engine Control Unit), Intake Air Temperature Sensor, Turbocharger System

System

Powertrain (Engine & Gearbox)

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Technical Description

P024B is set when the Engine Control Unit (ECU) detects that the Charge Air Cooler (CAC) bypass control valve is not responding correctly to commands or is stuck. The bypass system regulates intake air temperature by routing air either through the intercooler or bypassing it. This is essential for thermal management, combustion stability during cold starts, and DPF regeneration cycles. The ECU monitors the valve's position via a feedback sensor or by analyzing the duty-cycle and current draw of the actuator motor.

Possible Causes

Mechanical sticking of the bypass flap due to carbon buildup or oil residue

Faulty bypass valve actuator motor

Wiring harness damage, open circuit, or short to ground

Faulty Intake Air Temperature (IAT) sensor providing incorrect reference data

Symptoms

Check Engine Light (MIL) illuminated

Reduced engine performance (Limp mode may occur)

Rough idle during cold starts

Increased fuel consumption

Issues with DPF regeneration cycles

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P024B - Charge Air Cooler Bypass Control A Range/Performance

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P024B - Charge Air Cooler Bypass Control A Range/Performance

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