Code Definition

P1812 — TOT condition

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

About P1812

P1812 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.

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.

P1812 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 Transmission Oil Temperature (TOT) sensor is reading an implausible value outside the calibrated normal operating range. The TOT sensor is a thermistor, usually part of the internal transmission harness, and the TCM uses its reading for shift timing, line pressure control, and overheat protection. The fault may stem from a sensor failure, a wiring or connector issue, or a genuine condition where the fluid temperature is abnormally high or low. When set, the TCM may alter shift scheduling, inhibit torque converter lockup,...

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