P1135 code
 

My Wife's 2001 4Runner has CEL and VSC lights on. A scan shows P1135 which translates to Bank 1 Sensor 1 Heater circuit.

The car has 104,000 miles.

At this point I have disconnected the front A/F sensor and I measure about 2 ohms heater resistance. I also measured the source voltage and it is about 9.5 volts, measured across the heater pins.

I cleaned and reseated the connector and reset the code but it returns after the engine heats up or after driving less than a mile.

At this point I am in a quandary as to what to do. The sensor has never been replaced so it it probably due but the heater seems to be OK by the resistance measurement. Possibly the element could open up as it heats. I am not sure if this is a possible failure scenario.

I am assuming there is only one forward O2 (A/F) sensor in the 2001 4runner? I did check the rear one and it measured a higher heater resistance which I think is expected.

In checking through internet data on Toyota I see there is an A/F relay talked about. Is there one in the 2001 4runner?

Any help or guidance on where to go from here would be appreciated.

2 ohms sounds high unless you were wearing oven mitts. At that mileage and with that code it most likely is the A/F sensor.

Fixed
 

Yes, it was the Air Fuel (front) sensor. Replacing it was easy. New sensor came with a gasket. All is well now. Thanks.