Code Definition

P099C — Shift Solenoid G Control Circuit High (Shift Solenoid Valve SC)

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

About P099C

P099C is a generic (obd-ii standard) powertrain diagnostic trouble code recorded for Toyota vehicles. 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

Shift solenoid G, designated shift solenoid valve SC on Toyota transmissions, is an electro hydraulic valve in the valve body that routes pressurised fluid to the clutch packs and bands used to select a given ratio. The control module supplies the solenoid with battery voltage and completes the circuit by switching the ground side, monitoring the voltage on the control wire to confirm the solenoid is actually being driven. DTC P099C sets when the module sees that control circuit remaining at a high voltage when it should have been pulled low, which normally means the circuit is open, the solen...

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