P0712

P0712 sets when the TFT sensor circuit reads at or near 0V (typically below 0.15V for 5+ seconds), which the TCM interprets as the sensor shorted to ground or the signal wire shorted to chassis. The thermistor would have to read essentially zero ohms to produce this voltage, which is physically impossible unless the sensor element has shorted internally or the signal wire is grounded somewhere in the harness. Diagnostic ladder cheapest-first: unplug the trans case connector and check live data, if the temp reading jumps to -40F (the substitute value for an open circuit) then the fault is internal to the transmission (sensor or internal harness shorted to case); if the reading stays pinned at the max-hot value the short is external in the engine-bay harness between the case connector and the TCM. Ohm the signal wire to ground with the connector disconnected at both ends, anything under 100 ohms is a short. Verify the TCM 5V reference is healthy (4.95-5.05V) at the case connector, a collapsed reference rails the signal low and mimics a sensor short. Expensive misdiagnosis: do not authorize a solenoid-pack replacement until you have isolated the short to inside the transmission, an external harness short to ground (commonly at a chafe point near the trans cooler lines or starter) is a $80-200 repair versus a $1,500-2,500 internal job.

Vehicle-specific patterns: 2003-2007 Dodge Ram 1500 with 545RFE has a known internal harness chafe inside the trans where the lead-frame wire rubs through against a casting boss; 2007-2012 Hyundai Santa Fe/Sonata with A6LF1/A6MF1 throws P0712 from solenoid body internal short, the sensor is not individually serviceable; 2010-2015 Chevy Equinox/Terrain 2.4L with 6T40/6T45 sees P0712 alongside other solenoid codes when the TEHCM internal traces corrode from condensation, GM bulletin PIT5290 covers TEHCM replacement criteria. Estimated repair: $180 to $2,400.