Code Definition

P1874 — Transmission Automatic Hall Effect Sensor Power Circuit Failure

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Generic

About P1874

P1874 is a manufacturer-specific powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1874 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.

P1874 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

This DTC relates to the power supply circuit for a hall effect sensor used in the automatic transmission, such as a speed or position sensor. Hall effect sensors need a stable reference supply, typically 5V, and a good ground to produce an accurate digital signal. DTC P1874 sets when the transmission control module or PCM detects that the sensor power circuit is faulty from an open, a short to ground, or a short to battery. Without the correct supply the sensor cannot report, so the transmission may lose the affected speed or position input, shift harshly or incorrectly, and enter a fail safe ...

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