Code Definition

P1128 — Manifold Absolute Pressure (MAP) lower than expected

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

About P1128

P1128 is a manufacturer-specific powertrain diagnostic trouble code recorded for Acura vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1128 is stored, the module has detected a signal or supply voltage lower than the expected operating range.

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.

P1128 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 (MAP) sensor measures intake manifold pressure and reports it to the Engine Control Module (ECM) as a voltage signal, which the ECM uses to calculate engine load, fuel delivery, and ignition timing. DTC P1128 sets when the ECM detects that the MAP signal indicates a manifold pressure significantly lower than the value expected for the current throttle position, engine speed, and load, meaning the sensor is reporting more vacuum than conditions warrant. On Honda and Acura systems this reading is compared against throttle position and barometric pressure references...

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