Code Definition

P1823 — Transmission range switch P voltage low

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

About P1823

P1823 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 P1823 is stored, the module has detected a signal or supply voltage lower than the expected operating range; and 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.

P1823 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 voltage from the Park, or P, signal circuit of the transmission range switch is below its calibrated threshold, typically caused by a short to ground in the circuit. The Park signal is one of the coded range inputs and confirms to the module that the selector is in Park, which the starter interlock relies on. A low or invalid Park signal can cause a no start, incorrect gear indication, or altered shift logic if the module cannot trust the range information. The fault lies in the Park switch contact, its signal wiring, or...

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