P0241

Turbocharger Boost Sensor B Circuit Low

P0241 is a generic OBD-II powertrain diagnostic trouble code: Turbocharger Boost Sensor B Circuit 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
P0241
Group
Powertrain
System
Turbo/Boost
Severity
Warning (MIL on, possible limp mode)
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What P0241 means

P0241 is set when the ECM detects that the Boost Pressure Sensor B signal voltage has dropped below its minimum calibrated threshold — typically below approximately 0.2–0.4 volts — at a point in the engine's operating cycle where a low reading is not expected. This indicates the signal circuit has been pulled low, most commonly by a short to ground in the sensor wiring or within the sensor element itself. The ECM interprets this as a stuck-low or failed sensor and disables or severely limits boost control based on that sensor's input.

In practice, the most frequent cause is the sensor's internal element developing a short to the sensor body ground, or the signal wire chafing against metal bodywork, the exhaust manifold, or the turbo heat shield. Because the signal wire passes close to high-heat components, insulation damage is common on high-mileage turbocharged vehicles. The ECM will typically command reduced boost and activate the MIL; on some platforms the turbo is effectively disabled until the fault is cleared.

On twin-turbo setups, P0241 specifically implicates the Sensor B side (second turbocharger bank), so inspection should focus on the wiring routed to that bank. After any turbo upgrade or installation of an aftermarket boost controller, verify that the replacement sensor's voltage characteristics match the ECM's expected range, as a mis-specified sensor can output a valid-but-low voltage that the ECM interprets as a circuit-low fault.

Common causes

Most-frequently reported root causes when P0241 is logged.

  • 1
    Sensor B internal short to ground causing the signal wire to be pulled below minimum voltage.
  • 2
    Signal wire shorted to ground via chafing against the exhaust manifold, turbo housing, or chassis metal.
  • 3
    Corroded or collapsed connector pin creating a low-resistance path to ground.
  • 4
    Water or oil intrusion into the sensor connector causing a partial short.
  • 5
    Loss of the 5-volt ECM reference supply to the sensor (open reference circuit) making the signal appear low.
  • 6
    Aftermarket or incorrect replacement sensor with a different voltage characteristic outputting a sub-threshold signal.
  • 7
    Damaged or pinched wiring harness section between Sensor B and the ECM.

Symptoms drivers notice

Check Engine / MIL light illuminated.
Significant loss of power and boost — ECM disables or severely limits turbo output on the affected bank.
Vehicle may enter limp mode with boost capped at near-atmospheric levels.
Boost gauge reads low or near-zero even under full throttle.
On twin-turbo platforms, noticeable asymmetric performance loss from the Sensor B bank.
Code may be intermittent if the fault is a loose connector or position-sensitive wire chafe.

How to diagnose P0241

A typical diagnostic flow when this code is present.

  1. 1
    Scan for codes and note companions; a simultaneous Sensor A low code (P0237) suggests a shared 5-volt reference failure rather than an isolated Sensor B fault.
  2. 2
    With the key on and engine off (KOEO), back-probe the Sensor B signal pin: the reading should be approximately 0.5 V with the sensor connected and stable; below 0.2 V confirms a low-signal fault.
  3. 3
    Disconnect the Sensor B connector and re-measure the signal pin voltage at the harness side — if it rises back toward 5 V, the sensor itself is shorted internally; if it remains low, the harness wire is shorted to ground.
  4. 4
    Trace the Sensor B wiring from the connector to the ECM, looking for insulation damage, heat burns, or points where the harness contacts the exhaust or turbo housing.
  5. 5
    Measure the 5-volt reference supply at the sensor connector; an absent reference indicates an open circuit on the reference wire or a failed ECM reference driver.
  6. 6
    Replace Sensor B if an internal short is confirmed, or repair the harness if a grounded signal wire is found; reroute and protect the harness away from heat sources.
  7. 7
    Clear codes and verify with a full drive cycle including steady boost demand to confirm the fault does not recur.

Related powertrain codes

Frequently asked questions

What voltage should Boost Sensor B read and what indicates a fault?

A healthy sensor returns approximately 0.5 V at idle (near-atmospheric pressure) and rises to approximately 4.5 V at maximum boost. A reading consistently below 0.2-0.3 V with the engine running indicates a P0241 low-circuit condition, regardless of actual boost pressure.

If I unplug the sensor and the signal line voltage rises, what does that mean?

It strongly suggests the sensor itself is shorted internally. With the sensor disconnected, the signal line is floating or pulled toward the reference by the ECM's internal resistor, so a voltage rise confirms the sensor element was dragging the line low. A new sensor of the correct specification should resolve the low-circuit fault.

Can P0241 cause engine damage if ignored?

Indirectly, yes. With boost control relying on the sensor's input, the ECM running in a default or reduced-boost mode may cause the engine to run leaner or richer than intended under load. The underlying cause (chafed wiring near exhaust) may also worsen and create additional faults or an electrical fire risk.

Is P0241 related to the turbocharger hardware itself?

Not directly — P0241 is a circuit fault in the sensor or its wiring, not a mechanical turbo failure. However, a significant boost leak or oil carryover from the turbo can contaminate the sensor's pressure port and eventually damage the sensing element, leading to a circuit fault.

Disabling P0241 in software

RaceTune can permanently disable P0241 — 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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