Code Definition

P1156 — Manifold Absolute Pressure sensor open or shorted to ground

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Volkswagen

About P1156

P1156 is a manufacturer-specific powertrain diagnostic trouble code recorded for Volkswagen vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1156 is stored, the module has detected an open (broken or disconnected) electrical path in the monitored circuit; a short-circuit (voltage pulled to ground or to supply) in the monitored circuit; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P1156 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

The manifold absolute pressure sensor reports intake manifold pressure to the Engine Control Module (ECM), which uses it with other inputs to calculate load and set fuelling and ignition. DTC P1156 is stored when the ECM detects the manifold pressure circuit open or shorted to ground, so the signal voltage is missing or pulled to zero. With no valid pressure reading the ECM cannot calculate load correctly and falls back to a default strategy. Symptoms can include poor running, incorrect fuelling, lack of power, hard starting, and an illuminated check engine lamp with the engine possibly in lim...

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