Staff Answer
Jul 14, 2026 - 11:18 AM
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The P0845 code indicates a circuit malfunction related to the Transmission Fluid Pressure (TFP) sensor or switch "B." The transmission control module (TCM) or engine control unit (ECU) has detected an irrational, missing, or out-of-range electrical signal from this sensor, which is critical for determining correct gear shifting and hydraulic pressure control.
The most common causes for this condition include:
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Faulty Transmission Fluid Pressure Sensor/Switch B: The internal electronics of the sensor may have failed, leading to an erratic signal or a complete loss of data to the control module.
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Wiring and Connector Faults: Open circuits, shorted wires, or corroded pins in the connector leading to the TFP sensor "B" can disrupt the signal, causing the controller to register the fault.
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Dirty or Contaminated Transmission Fluid: Excessive debris or metallic particles in the transmission fluid can clog the hydraulic passages or interfere with the sensor’s ability to detect fluid pressure accurately.
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Internal Transmission/Valve Body Issues: If the valve body is worn or there are significant internal hydraulic leaks, the pressure sensor may not register the expected pressure changes, triggering the circuit code.
To diagnose this, start by checking the transmission fluid condition and level. Inspect the wiring harness near the transmission for damage, and verify that the connector pins are clean and free of corrosion. If the external checks are clear, testing the sensor’s electrical output with a multimeter or an OBD-II scanner's live data function is necessary to confirm if the sensor has failed.
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