P1155

P1155 is the Bank 2 mirror of P1135 and indicates a heater circuit fault on the upstream AFR sensor for Bank 2 Sensor 1, which on transverse Toyota V6 engines is the rear (firewall-side) sensor and on longitudinal V6 or V8 platforms is the passenger side. The diagnostic ladder is identical to P1135 but with one critical Bank 2 wrinkle: on 2GR-FE and 3MZ-FE engines, Bank 2 Sensor 1 sits directly behind the engine against the firewall and is bathed in radiated exhaust heat from the rear manifold, which is why it statistically fails years before Bank 1. Begin by reading live AFR heater current in Mode 06 or via Techstream (specification is 0.2 to 2.0 A, with most healthy sensors landing near 1.0 A at steady state); a flat 0.0 A reading points to an open circuit, while a pegged-high reading points to a shorted heater element. Verify the heater fuse and relay before condemning the sensor. The costly mistake here is pulling the intake manifold to reach Bank 2 only to discover the fault was a chafed wire at the bracket, or replacing the sensor with a cheap universal four-wire unit that lacks the calibration resistor Toyota's PCM expects.

Vehicle-specific patterns: Toyota 2GR-FE 3.5L V6 (Camry, Avalon, Sienna, Venza, Highlander 2007-2014) is the dominant P1155 platform; the rear Bank 2 sensor typically fails at 80k to 120k miles, and the upper intake plenum must be removed for access, which is why labor dominates the bill. Toyota 3MZ-FE 3.3L V6 (Sienna, Highlander, Camry, Lexus RX330 2004-2007) shows the same rear-bank early-failure pattern; Denso 234-9009 is the correct OE part for many of these. Toyota 1GR-FE 4.0L V6 (Tacoma, 4Runner, FJ Cruiser 2005-2015) sees P1155 more often from harness chafe at the rear bank than from sensor death. Toyota 2UZ-FE 4.7L V8 (Tundra, Sequoia, Land Cruiser 2000-2009) sets P1155 most commonly from a failed EFI main relay or corroded ground at the rear head. Estimated repair: $40 to $620.