P0249

Turbocharger Wastegate Solenoid B Low

P0249 is a generic OBD-II powertrain diagnostic trouble code: Turbocharger Wastegate Solenoid B Low. It is logged by the engine control unit when the turbo/boost monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P0249
Group
Powertrain
System
Turbo/Boost
Severity
Warning (MIL on, possible limp mode)
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What P0249 means

P0249 is set when the PCM detects a lower-than-expected voltage on the turbocharger or supercharger wastegate solenoid "B" control circuit. Like P0245 on the solenoid A circuit, P0249 indicates either an open coil inside the solenoid B itself, a broken or shorted-to-ground wire in the solenoid B harness, or a corroded connector that prevents the PCM from delivering its PWM signal to the secondary wastegate solenoid.

On twin-turbo platforms — BMW N54, N63, S63, Audi 4.0T biturbo, Ford 3.5L twin-turbo EcoBoost — each turbocharger has its own wastegate solenoid. P0249 specifically affects solenoid B (secondary or rear-bank turbo), so the primary turbo continues to operate normally. The secondary turbo's wastegate defaults to a fail-safe position (typically open), cutting the contribution of the second turbocharger to boost pressure and producing a noticeable reduction in upper-end power. The engine may enter limp mode or a single-turbo operation strategy.

Diagnosis follows the same sequence as P0245: visual harness inspection first, followed by solenoid coil resistance measurement, supply voltage verification, and harness continuity testing. Because the solenoid B harness often runs alongside the secondary turbocharger's hot side, heat-related insulation failure is a common cause on high-mileage vehicles. Replacement of the solenoid is straightforward once the electrical fault is confirmed.

Common causes

Most-frequently reported root causes when P0249 is logged.

  • 1
    Open coil inside wastegate solenoid B (broken winding causing high resistance or no continuity).
  • 2
    Short to ground in the solenoid B control wire draining the circuit voltage below the PCM threshold.
  • 3
    Broken, chafed, or heat-damaged wire in the solenoid B harness, particularly near the secondary turbo hot side.
  • 4
    Corroded, pushed-back, or loose terminal in the solenoid B connector.
  • 5
    Failed PCM output driver on the channel dedicated to solenoid B.
  • 6
    Physical damage to the solenoid body from contact with the turbine housing or adjacent components.
  • 7
    Water or oil ingestion into the solenoid connector causing a leakage path that pulls the circuit low.

Symptoms drivers notice

MIL illuminated with P0249 stored.
Reduced boost pressure particularly in the upper RPM range where the secondary turbocharger normally contributes.
Noticeably asymmetric power delivery on biturbo engines — adequate low-end torque but weak peak power.
Engine enters a single-turbo or reduced-boost operating strategy (limp mode possible).
Sluggish acceleration above approximately 3,000–4,000 RPM depending on the biturbo sequencing strategy.
Companion code P0247 (solenoid B malfunction) may also be stored if the PCM logs both the circuit fault and the boost deficiency.

How to diagnose P0249

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, retrieve all stored DTCs, and review live boost pressure data to confirm the secondary turbo's contribution is reduced.
  2. 2
    Locate solenoid B — on BMW N54/N63 it is on the rear turbocharger; on the Ford 3.5L EcoBoost it is on the passenger-side turbo assembly.
  3. 3
    Visually inspect the solenoid B connector and harness, paying particular attention to sections routed near the turbo hot side for heat-related insulation damage.
  4. 4
    Unplug the solenoid connector and measure coil resistance; an open circuit (infinite resistance) or unusually high reading confirms a failed solenoid.
  5. 5
    With ignition on and solenoid unplugged, verify correct supply voltage on the harness side; then check continuity of the control wire from the connector back to the PCM.
  6. 6
    Clean the connector terminals with electrical contact cleaner, re-seat the connector, clear the DTC, and road-test before ordering parts — intermittent connection issues are the most common cause.
  7. 7
    If the solenoid tests open or shorted, replace it; if wiring is damaged, repair or replace the affected section before replacing the solenoid.

Related powertrain codes

Frequently asked questions

Is P0249 the same fault as P0245 but on the second turbo?

Functionally, yes. Both are circuit-low voltage codes for their respective solenoids (A and B), and the diagnostic approach is identical. The distinction matters on twin-turbo engines because the physical location differs — solenoid B is typically on the secondary turbocharger — and finding the correct harness routing is the first challenge.

Can P0249 cause overboost as well as underboost?

P0249 is a circuit-low fault, which means the solenoid cannot be energised and the wastegate defaults open, causing underboost. Overboost is the risk associated with P0246/P0250 (circuit-high faults). If you have both P0249 and an overboost condition, check for a separate solenoid A fault or a stuck wastegate valve.

On the BMW N54, how accessible is solenoid B?

The N54 rear turbocharger solenoid is more accessible than the front unit but still requires removal of the engine cover, intake duct, and possibly the charge-air cooler duct for clear access. The solenoid itself unclips quickly once accessible; most of the labour involves reinstallation and leak testing.

Will the car pass emissions with P0249 active?

No — an active MIL for any emission-relevant code is an automatic emissions test failure in most jurisdictions. Even though P0249 is primarily a boost management fault, the stored DTC and illuminated MIL will cause a fail until the code is resolved and the MIL clears after the required number of drive cycles.

Disabling P0249 in software

RaceTune can permanently disable P0249 — 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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