Code Definition

P1826 — Transmission range switch C voltage high

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

About P1826

P1826 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 P1826 is stored, the module has detected a signal or supply voltage higher 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.

P1826 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 on the Transmission Range Switch C signal circuit is higher than its calibrated maximum threshold, typically caused by an open circuit or a short to voltage. Range Switch C is one of the coded contacts the TCM reads together to determine the gear selector position. A high reading at the wrong time gives the module an invalid range combination, which can cause incorrect gear indication, altered or inhibited shifting, no reverse lamps, or a no start when Park or Neutral cannot be confirmed. The fault lies in the sw...

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