P1121

P1121 on a Toyota specifically means the Coolant Bypass Valve (CBV) position switch is out of range — this code only shows up on Toyota's 2GR-FXE hybrid V6 (2008-2016 Highlander Hybrid, 2006-2008 Lexus RX400h, 2010-2015 RX450h) where a coolant-flow bypass valve routes coolant around the heater core when the engine cycles off during hybrid operation. The position switch reports valve state to the hybrid ECU; when the switch's reported position disagrees with commanded position for more than ~10 seconds, P1121 sets and the hybrid system loses heater function. Cheapest-first ladder: (1) scan live data for CBV position-switch state — a healthy switch reads a clean two-state signal (typically 0V closed / 5V open or vice versa per FSM) with no rapid bouncing; if the signal is stuck at one rail or floating mid-range (2-3V) the switch contacts are corroded or the valve is mechanically stuck. (2) Pull the connector at the bypass valve and check for coolant intrusion — a green/blue crust on the pins is the most common failure mode, since the valve sits in a low spot in the coolant circuit and the connector seal degrades. Clean the pins, dielectric-grease them, and clear the code before condemning the valve. (3) Manually actuate the valve with a scan tool's bidirectional control (if your tool supports Toyota Techstream-level commands) and confirm the switch state changes within 2-3 seconds of command. Expensive-misdiagnosis caveat: don't replace the entire CBV assembly ($350-$550 part on the 2GR-FXE) before confirming the failure isn't just connector corrosion — a $0 cleanup plus a $4 packet of dielectric grease fixes roughly half of P1121 sets on this engine family.

Vehicle-specific patterns: 2008-2016 Toyota Highlander Hybrid with the 2GR-FXE 3.3L/3.5L V6 is the dominant P1121 platform — the bypass valve sits behind the timing cover area and the connector pools road salt and coolant weep, so corrosion is the failure mode of choice north of the Mason-Dixon line. 2006-2008 Lexus RX400h and 2010-2015 RX450h share the same valve and the same corrosion pattern; Lexus shops typically clean the connector once and replace the valve on the second visit. 2012-2017 Toyota Camry Hybrid and Avalon Hybrid use a different coolant-management strategy (no separate CBV switch) and won't throw P1121 — if the code shows on a hybrid Camry, scan-tool VIN-decode first because the code definition may have remapped to a different fault on that platform. Estimated repair: $80 to $650.