Code Definition

P1212 — Mass Airflow circuit intermittent low

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

About P1212

P1212 is a manufacturer-specific powertrain diagnostic trouble code recorded for GM vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1212 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.

P1212 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 mass air flow sensor reports the mass of air entering the engine to the Engine Control Module (ECM), which uses that value as the primary input for injector pulse width and spark timing. DTC P1212 is set when the ECM sees the air flow signal drop intermittently to a level that is implausibly low for the current throttle position, engine speed and manifold pressure, then recover to normal. A momentary loss of the air flow signal makes the ECM briefly calculate a much smaller fuel requirement than the engine actually needs, so the engine goes sharply lean for an instant. Because the fault is...

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