Code Definition

P1825 — Transmission range switch A, B, C & P signals invalid

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

About P1825

P1825 is a manufacturer-specific powertrain diagnostic trouble code recorded for GM vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1825 is stored, the module has detected a plausibility fault — the measured value is in the electrical range but is not consistent with expected operating behaviour.

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.

P1825 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 sets when the Transmission Control Module (TCM) detects that the combined signals from transmission range switch circuits A, B, C, and P form an invalid or undecodable gear position pattern. The TCM expects specific combinations of high and low voltage states across these circuits to correspond to valid selector positions such as Park, Reverse, Neutral, and Drive. An invalid combination indicates signal conflicts, a missing input, or a fault within the switch or its circuits. The result can be incorrect gear indication, default or fail safe shift behaviour, no reverse lamps, and in so...

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