P022B

Charge Air Cooler Bypass Control A Circuit Low

P022B is a generic OBD-II powertrain diagnostic trouble code: Charge Air Cooler Bypass Control A Circuit Low. It is logged by the engine control unit when the fuel/inj monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P022B
Group
Powertrain
System
Fuel/Inj
Severity
Warning (MIL on, possible limp mode)
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What P022B means

P022B is set when the engine control module (ECM) detects a lower-than-expected voltage or current value in the "A" circuit that drives the charge air cooler (intercooler) bypass control actuator or solenoid valve. The charge air cooler bypass valve allows the ECM to route turbo-compressed intake air either through or around the intercooler, enabling faster intake temperature management during cold starts and transient load changes. The ECM monitors the control circuit for out-of-range electrical feedback and logs P022B when the signal falls below the minimum threshold for the commanded duty cycle or position. In practice this usually means the circuit is pulling less current than expected — indicating a partially open wiring path, increased resistance from corrosion, a failing actuator coil, or a defective driver stage inside the ECM itself. On many turbocharged petrol and diesel applications the bypass valve is a vacuum- or motor-driven flap; when the ECM loses authority over it the boost circuit operates in a fixed or default position, degrading drivability and potentially triggering a power-derate. Left unaddressed, an uncontrolled bypass valve causes persistent charge-air temperature deviations that affect fuelling calculations and combustion efficiency across all operating conditions.

Common causes

Most-frequently reported root causes when P022B is logged.

  • 1
    Charge air cooler bypass actuator or solenoid coil failure causing abnormally low current draw on the control circuit
  • 2
    Bypass valve stuck in open or closed position due to mechanical binding, carbon buildup, or damaged flap mechanism
  • 3
    Damaged, chafed, or broken wiring in the bypass control harness producing high resistance or an intermittent open
  • 4
    Corroded or loose connector pins at the bypass valve or ECM harness connector reducing circuit conductivity
  • 5
    Blown fuse or failed relay supplying power to the bypass control circuit
  • 6
    Obstruction in the bypass valve's range of motion preventing full actuation and causing abnormal load on the driver circuit
  • 7
    ECM internal driver fault for the bypass control output (rare; only after all external circuit faults are ruled out)

Symptoms drivers notice

MIL (Check Engine Light) illuminated with P022B stored, often alongside related boost or charge-air temperature codes
Reduced engine power and throttle response, particularly noticeable during acceleration under boost
Vehicle entering limp or power-derate mode as the ECM limits boost output when charge-air bypass control is lost
Engine misfiring or rough running caused by uncorrected charge-air temperature affecting air/fuel ratio calculations
Poor fuel economy as combustion efficiency deteriorates with uncontrolled intake charge temperature
Sluggish cold-start performance if the bypass valve is fixed in the through-cooler position and the intercooler cannot be bypassed during warm-up

How to diagnose P022B

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, retrieve all stored codes and freeze-frame data, and note any companion codes relating to boost pressure, charge-air temperature, or turbocharger control that help localise the fault
  2. 2
    Visually inspect the charge air cooler bypass valve and actuator for obvious mechanical damage, stuck flap, carbon deposits, or broken linkage
  3. 3
    Inspect the bypass valve wiring harness from the connector to the ECM for chafing, heat damage, corrosion, or broken terminals; reseat connectors and check for pushed-back pins
  4. 4
    Using a DVOM, measure resistance across the bypass actuator solenoid coil terminals and compare to the manufacturer specification; a reading significantly higher than spec confirms coil degradation
  5. 5
    Check the relevant fuse and relay for the bypass control circuit; replace any blown fuse and verify the underlying circuit does not have a short to ground before installing a new fuse
  6. 6
    Use the scan tool's actuator test or live data to command the bypass valve to open and closed positions while monitoring the commanded vs. actual position or duty cycle feedback
  7. 7
    If wiring and mechanical components test within spec, suspect and test the ECM output driver using a manufacturer-level diagnostic tool before condemning the module

Related powertrain codes

Frequently asked questions

Can I still drive with a P022B code active?

Short trips are generally possible but not advisable. The ECM may enter a power-derate or limp mode to protect the engine, and running without proper charge-air bypass control over extended periods can lead to elevated intake temperatures, increased knock risk, and accelerated wear on turbocharged components.

Is P022B the same on petrol and diesel turbocharged engines?

The circuit diagnostic logic is the same — the ECM measures control circuit voltage against a threshold — but the physical bypass valve design differs. Petrol intercoolers often use a vacuum-actuated or motorised flap, while diesel systems may use a solenoid-controlled valve. Always consult the vehicle-specific wiring diagram for correct resistance and voltage specifications.

What is the difference between P022B (Circuit Low) and P022C (Circuit High)?

P022B indicates the electrical signal is below the expected range, typically pointing to an open circuit, high resistance, or underperforming actuator coil. P022C indicates the signal is above the expected range, more commonly caused by a short to voltage in the control wiring or an ECM driver fault producing excessive output.

How much does it typically cost to repair P022B?

Cost varies widely by root cause. Connector cleaning or harness repair may cost under $100 in labour. A replacement bypass actuator or solenoid typically runs $80–$250 in parts plus 1–2 hours of labour. ECM replacement is rare and expensive; exhaust all wiring and mechanical diagnoses first.

Disabling P022B in software

RaceTune can permanently disable P022B — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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