P1135 Fault in 2001 Toyota Highlander: What Does It Mean and How to Fix Transmission Limp Mode?
My 2001 Toyota Highlander is displaying a P1135 diagnostic code. The vehicle starts and runs smoothly initially, but after driving just a short distance—typically less than one-quarter mile—it begins to lose forward movement. The engine continues to idle normally and maintains smooth RPMs during acceleration, yet the transmission fails to move. I'm concerned about whether this is related to limp mode or another underlying issue. The P1135 code indicates an 'Air/Fuel Sensor Heater Circuit Response' fault on Bank 1 Sensor 1. However, I have already replaced multiple components including all O2 sensors, throttle body, idle air control valve, mass airflow sensor, fuel filter, and transmission-related sensors (such as camshaft position and speed sensors). The vehicle runs well in park and at idle but fails to shift into forward gears under load. Recently, additional codes P141 and P1155 have appeared. I'm seeking clarification on whether the P1135 code directly causes transmission failure or if it's a symptom of another issue such as faulty temperature sensing or sensor heater circuit malfunctions.
The P1135 code refers to an Air/Fuel Sensor Heater Circuit Response (Bank 1, Sensor 1) and is not directly linked to transmission loss. This fault typically affects the oxygen sensor heater circuit and does not cause limp mode or transmission failure on its own.