Code Definition

P0099 — Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0099

P0099 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0099 is stored, the module has detected 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.

Because P0099 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The P0099 code indicates an intermittent or erratic signal in the circuit of the Intake Air Temperature (IAT) Sensor 2. This sensor measures the temperature of air entering the engine's intake system, and its data is essential for the Engine Control Module (ECM) to optimise fuel delivery, ignition timing, and overall engine performance. The ECM sets this code when it detects irregular or inconsistent signals from the IAT Sensor 2, suggesting issues with the sensor's operation or connectivity.

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