Code Definition

P0977 — Shift Solenoid B Control Circuit High

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

About P0977

P0977 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 P0977 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 P0977 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 P0977 fault code is set when the control module detects a high voltage condition in the control circuit of Shift Solenoid B. This solenoid is crucial in the operation of automatic transmissions, where it regulates the flow of hydraulic fluid for gear engagement and disengagement. A high voltage condition in this circuit typically indicates an electrical fault, such as a short to power or an internal defect within the solenoid. High voltage can lead to overactivation or malfunctioning of Shift Solenoid B, which may result in transmission issues such as harsh or erratic shifting, slipping ge...

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