P0135 fault code ,fuel system 1 OL_ fault

Just picked up a 03 taco about a week ago, has p0135 dtc. Idles and runs a little rough. Hooked up my scan tool to look at freeze data and it shows fuel system 1 OL_fault. Anyone have this issue before? I dont wanna just throw parts at it

 

I’d run a fuel injector cleaner and spray some carb cleaner around your intake gasket and see if you have a leak. Check your plugs as well..

 

the simple answer is the heater circuit in the sensor, it could be a Air fuel sensor or an Oxygen sensor, isnt reading correctly. There is a resistor coil in the sensor that immediatly starts to heat up when you turn the motor on so that when the PCM goes into closed loop the PCM starts adjust A/F ratios. There are 4 wires to this sensor 2 are for the heater circuit and 2 are for the A/F readings.

Attached is the FSM for wiring. All you will need is a test ligt and a volt ohm meter. You will check for +12v where it is supposed to be and if it is there then check resisitance across the sensors heating element.

If you need to replace the sensor get it from a reputable source as there are fakes out there. if there is an issue after you install the bargain unit you are chasing your tail because it is a new part... it should work... so you are off loading the parts cannon when all along it is just a bad "new" part.