P2A0A: Manifold Absolute Pressure Sensor B Circuit
What to do
Expect reduced power, poor economy, and possibly black smoke under acceleration. The car will usually still drive. On a turbocharged engine, ask whether the charge pipework has been checked — a loose or split pipe between the turbocharger and the engine produces the same readings as a failing sensor and is far cheaper to find.
What this code means
The circuit for the second manifold absolute pressure sensor is faulty.
A second manifold absolute pressure sensor is not a spare, and what it is for depends on where it sits.
A MAP sensor measures the pressure of the air actually in the manifold, which on a naturally aspirated engine is the primary measure of how hard it is working. On a turbocharged engine one sensor is no longer enough, because there are two pressures worth knowing: what the turbocharger produced, and what reached the cylinders after the intercooler and the throttle.
The difference between the two is the diagnosis. A healthy boost pressure with a low manifold pressure means the restriction is between them — a blocked intercooler, a throttle not opening, or a charge pipe that has come adrift. Neither sensor alone can distinguish that from a turbocharger that is simply not producing.
On some installations sensor B serves a second bank instead, and then the comparison is left against right rather than before against after. The vehicle's own documentation is the only authority on which arrangement it uses, and getting it wrong sends the diagnosis to the opposite end of the engine.
Because the module cross-checks MAP against airflow, throttle angle and engine speed, a drifting sensor is caught early — which is why the Range/Performance variant is the common one here and an outright circuit failure is not.
The base circuit fault: no plausible signal.
Likely causes
Start here
- Faulty manifold absolute pressure sensor · moderate
- Blocked or split MAP sensor vacuum hose · easy
- Corroded or loose connector · specialist
Less common
- Boost leak in charge pipework · moderate
- Failed sensor reference voltage supply · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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