P024B

What it means

P024B means the engine control unit has detected that the charge air cooler bypass control 'A' is stuck, so it is not moving to the position the ECU commands. The bypass diverts intake air around the charge air cooler on some turbocharged or supercharged engines. The ECU sets the code when position feedback, or the resulting intake air temperature and boost behaviour, does not match the commanded state. How the bypass is built and monitored varies by model and engine.

Symptoms

• Malfunction indicator lamp on
• Reduced power or the engine going into limp mode
• Poor throttle response or hesitation under boost
• Higher than normal intake air temperature or knock-related power loss
• Rough running or poor performance when cold, or heat-related power loss when hot

Possible causes

• Bypass valve or flap mechanically seized or sticking from carbon, oil or debris build-uplikely
• Faulty bypass actuator (electric motor, vacuum or solenoid type depending on design)likely
• Wiring or connector fault in the actuator or position feedback circuit, such as corrosion, chafing or poor pin tensionpossible
• Vacuum supply leak or damaged vacuum line or control solenoid, on systems that use vacuum actuationpossible
• Faulty position sensor or intake air temperature sensor giving a false reading of the bypass statepossible
• Linkage or actuator arm disconnected or broken, or the valve housing damagedrare
• ECU fault or outdated software, where the manufacturer has identified one for that modelrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting engine load, intake air temperature, boost and coolant temperature when the code set; check for related boost, intake temperature or actuator codes.
2. Look up the manufacturer's service information for the exact bypass design on this model and engine, and any technical bulletins.
3. Visually inspect the bypass actuator, linkage, wiring and connectors for damage, corrosion, oil contamination or loose fittings.
4. If vacuum operated, check the vacuum lines, reservoir and control solenoid for leaks, splits or blockages.
5. Using a scan tool with bidirectional controls, command the bypass open and closed and watch the actual position or feedback value and listen or feel for actuator movement.
6. Check the actuator supply, earth and signal circuits with a multimeter or oscilloscope against the wiring diagram, including voltage drop under load.
7. Remove the valve or inspect through the intake ducting if accessible to check for a seized flap, carbon or oil build-up and free movement by hand.
8. Compare intake air temperature before and after the cooler against expected values to confirm the bypass is really stuck.

How to fix

• Clean or replace a seized or contaminated bypass valve assembly, and find the source of any oil or carbon contamination.
• Replace the faulty actuator or solenoid, then carry out any adaptation or relearn the manufacturer specifies.
• Repair or replace damaged wiring, terminals or connectors in the actuator and feedback circuits.
• Replace split or leaking vacuum lines and any faulty vacuum control component.
• Replace a faulty position or temperature sensor once testing confirms it is at fault.
• Update the ECU software only if the manufacturer lists an outdated calibration as a known cause for this vehicle.

Can I keep driving?

Nearby codes

• P024AGenericCharge Air Cooler Bypass Control A Range/Performance
• P024CGenericCharge Air Cooler Bypass Position Sensor A Circuit