Code Definition

P099C — Shift solenoid G circuit high

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

About P099C

P099C 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 P099C is stored, the module has detected a signal or supply voltage higher 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.

Because P099C 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 fault code P099C is set when the Engine Control Module (ECM) or Transmission Control Module (TCM) detects a high voltage condition in the circuit of shift solenoid G. This solenoid is an essential component of the transmission's hydraulic control system, responsible for managing the flow of transmission fluid for proper gear selection and engagement. A high voltage in the solenoid's circuit may suggest an electrical issue such as a short to power, excessive power supply, or an electrical overcharge, which can negatively impact the solenoid's operation. This condition can lead to various tr...

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