P012B
Turbocharger/Supercharger Inlet Pressure Sensor Circuit Range/Performance (Downstream of throttle valve)P012B is a generic OBD-II powertrain diagnostic trouble code: Turbocharger/Supercharger Inlet Pressure Sensor Circuit Range/Performance (Downstream of throttle valve). 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.
What P012B means
Code P012B is set when the powertrain control module (PCM) detects that the turbocharger or supercharger inlet pressure sensor, located downstream of the throttle valve, is producing a signal that falls outside the expected range or does not change in proportion to actual operating conditions. This downstream sensor sits between the throttle body and the intake manifold and gives the PCM real-time data on the pressure of air being forced into the engine. The PCM uses this data to precisely calculate air mass, trim boost pressure, and determine correct fuelling. A range/performance fault means the sensor is electrically functional (not open or shorted) but its output is implausible — either stuck at a fixed value or not tracking throttle and boost events as expected. This often results in the PCM switching the engine into a reduced-power limp mode to prevent damage. Because the sensor wiring typically runs through high-temperature engine bay areas, heat-induced insulation breakdown is a frequent root cause alongside sensor contamination or connector corrosion.
Common causes
Most-frequently reported root causes when P012B is logged.
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1
Defective or contaminated turbocharger/supercharger inlet pressure sensor
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2
Damaged, chafed, or heat-degraded sensor wiring harness
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3
Corroded or loose sensor connector pins
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4
Clogged or severely restricted air filter reducing measurable pressure range
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5
Vacuum or boost leak between throttle body and intake manifold
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6
ECM/PCM internal fault causing incorrect sensor signal interpretation
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7
Blown fuse in the sensor reference voltage circuit
Symptoms drivers notice
How to diagnose P012B
A typical diagnostic flow when this code is present.
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1
Connect an OBD-II scanner, record all DTCs and freeze frame data, then clear codes and confirm P012B resets under normal driving
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2
Visually inspect the inlet pressure sensor, its connector, and the wiring harness for fraying, heat damage, chafing, or corrosion (green discoloration on pins)
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3
Check all relevant fuses in the engine and interior fuse boxes for the sensor reference voltage circuit
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4
Inspect the air filter for heavy restriction or collapse; replace if clogged
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5
Inspect all boost and vacuum hoses between the turbo/supercharger outlet, throttle body, and intake manifold for cracks or loose clamps
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6
Using a multimeter, verify sensor supply voltage (typically 5 V reference), ground integrity, and signal voltage across the operating range
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7
If wiring and connections test good, substitute a known-good pressure sensor and retest; replace ECM only after all other causes are ruled out
Related powertrain codes
- P003A — Turbocharger/Supercharger Boost Control A Position Exceeded Learning Limit
- P003B — Turbocharger/Supercharger Boost Control B Position Exceeded Learning Limit
- P0045 — Turbocharger/Supercharger Boost Control A Circuit/Open
- P0046 — Turbocharger/Supercharger Boost Control A Circuit Range/Performance
- P0047 — Turbocharger/Supercharger Boost Control A Circuit Low
- P0048 — Turbocharger/Supercharger Boost Control A Circuit High
Frequently asked questions
Can I drive with P012B active?
Short distances are possible if the vehicle is not in limp mode, but continued driving risks running an incorrect air/fuel ratio that can damage the catalytic converter or turbocharger. Address the fault promptly.
Is P012B the same as a MAP sensor fault?
Not exactly. The downstream turbo inlet pressure sensor and the intake manifold absolute pressure (MAP) sensor can be the same physical unit on some vehicles, but on others they are separate. P012B specifically targets the downstream turbo inlet circuit, while MAP sensor codes (P0106–P0108) target the manifold sensor circuit.
Why does this code appear after an air filter service?
A partially dislodged air duct or incorrectly seated filter housing can introduce an unmetered air leak downstream, causing plausibility errors on the inlet pressure sensor. Always verify all clamps and couplings are fully tightened after any intake service.
Will replacing the sensor always fix P012B?
Not always. Because this is a range/performance code rather than a pure circuit fault, wiring damage, connector corrosion, or a vacuum leak can produce the same plausibility failure. Confirm wiring and boost circuit integrity before condemning the sensor.
Disabling P012B in software
RaceTune can permanently disable P012B — 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.
ECU families we can disable P012B on
We hold the DaVinci A2L disable definitions for these families, so the exact P012B path and mask addresses are mapped. verified marks a confirmed disable definition. We support many more — upload your file and our identifier will match it automatically.
- Bosch EDC17C66 verified
- Bosch EDC17CP44 verified
- Bosch EDC17CP57 verified
- Bosch MG1CP002 verified
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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