Code Definition

P0991 — Transmission Fluid Pressure Sensor/Switch E Circuit Intermittent

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

About P0991

P0991 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 P0991 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 P0991 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 P0991 fault code is activated when the control module detects intermittent signals in the Transmission Fluid Pressure Sensor/Switch E Circuit. This sensor or switch is vital for monitoring the hydraulic pressure within a specific part of the transmission system. An intermittent fault indicates that the signals from the sensor or switch to the control module are irregular, sporadic, or failing to maintain a consistent connection. This intermittent behaviour can be due to loose connections, corroded terminals, intermittent shorts in the wiring, or issues within the sensor or switch itself. S...

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