Hi there, I am an Old Tech , that recently acquired a 2003 Camry 2.4L4. I received this vehicle, because my Nephew checked the coolant in my o6 PT Cruiser and did not secure the System Cap. He then proceeded to drive several miles until the Car burned up the engine. So, he gave me the Camry. It's a 2003 CAL/FED ULEV Vehicle. I came to these Forums because I am at a dead end on the Diag, atm. Haynes/Chilton manual does not have the wiring Diagrams for the Engine/Emissions Circuits. I have a P0031 DTC and am trying to find the EFI or Heated O2 Sensor Fuse and relay. It's not a failed sensor , other people have been into the car problem, and now I just want to fix it right. I checked what is listed as the EFI Fuse in the Underhood Block. It was in good condition. I suspect a Relay or Wire issue. Any help would be deeply appreciated. I am basically walking , at this time.

 

The A/F heater relay is located in fuse/relay box driver side engine compartment closest to the strut tower.

There are several rows of relays 1,2,3 and a row of fuses 4. The relay is first relay in row 1 on the same side of the box that has the two high current fuses (bolted to the board) in row 4 at its end. Look for the high current fuses then look across to the opposite corner of the box.

The A/F heater relay 25A fuse is in other "box" below the one with the relay. It should be labeled. Its a conventional blade fuse. Location is the upper corner. Its the only blade fuse of 4 rows of blade fuses that is closest to a corner.

Sensor wiring is.
Black/white wire is B+ from A/F relay. B+ is battery voltage.
Brown is ground and also ground for any shielded wires to the sensor
Black goes to computer and sends the signal. This wire is shielded.
Blue is for heater goes to computer..

The heater and signal wires go to a junction box behind the drivers side kick panel (you me be able to hit with your left knee when sitting) then to the ECU.

With engine at 2500 rpm for 90s the signal between brown and black wires should be a pulse signal. You made an oscilloscope to check it.

Engine at idle check voltage between blue and brown wire. Should be 9 to 14v. With ign switch on engine off below 3v.

 

I appreciate the info. I went ahead and ordered a Toyota Factory Wiring Diagram Manual, and am sharpening the ends , on my DVOM. I will keep you posted, on what I find. I suspect a wire repair.

 

Good luck and let us know how you do.