P0044

P0044 is the 'circuit high' version of the bank-1 sensor-3 heater fault - the heater control signal is stuck above the upper electrical threshold or showing implausible current flow indicating a short-to-power. Diagnostic logic mirrors P0043 but inverted: instead of looking for shorts-to-ground or open circuits, look for shorts-to-battery or shorts to a 12V circuit anywhere in the harness between PCM and sensor. Cheapest-first ladder: (1) Unplug the sensor and DMM the heater control pin to ground - a stuck-high reading with the sensor disconnected confirms harness short to power; a floating or zero reading means the sensor itself is the failure. (2) Inspect the harness route under the vehicle for chafing against frame rails, body brackets, or against the exhaust pipe itself. (3) Check sensor heater coil resistance - a partially shorted internal coil can pull excessive current and read as a short-to-power fault. The 20-minute DMM sequence catches harness-vs-sensor cleanly.

Vehicle-specific patterns: 2007-2014 Toyota Tundra / Sequoia 5.7L throws P0044 from chafed underbody harness at the body-mount near the bank-1 third O2 sensor. 2008-2014 Lexus GX460 / LX570 with the 5.7L throws P0044 from a known harness retainer issue that lets the wire rub against the frame. 2010-2016 Toyota Sienna with the 2GR-FE throws P0044 from melted insulation when the underbody heat shield falls off. 2011-2018 Lexus IS350 / GS350 with the 2GR-FSE throws P0044 from a failed heater coil internally on the rearmost sensor. Estimated repair: $60 to $380