Ok, first of all. I have searched this with no help yet..... ok, 92 pickup, auto, 22re, 2wd ext cab. I bought an after market O2 sensor and it did not come with a wiring diagram and I am lost!!! The new sensor has (1) white, (1) purple, (1) black, (1) grey. I have found on another site where is states, the following.

Black- signal
Grey- ground
Purple- heater
White- heater.


I've tried every hooking it up like it calls for, but now I am getting code 21, any help would be great! Thanks guys.

 

Maybe this would help, I have black to black harness side. Gray to brown harness side. The white and purple can go to either white/red harness side or pink/green harness side. If this correct you may have bad heater resistor to pop instant 21. Let me know.

 

On the truck side, Black and Brown is the sensor, Green/Black and White/Red is the heater.

On the sensor side, the two heater wires are 5-7 ohms, the others should all be open.

As Thelast83inNJ says, code 21 mean EITHER an open or short in the heater, or bad signal from the sensor once it's warmed up. Since you're getting the code right away it's pretty clear you don't have the heater connected correctly. So check for the correct resistance on the new sensor, and if that doesn't help, check for 12v to ground on White/Red.

I hope you got a good deal; if they use non-Toyota colors and won't tell what they are ...

 

well, I went out and wired it up correctly, I think. Still getting the code 21, I read in my Haynes manual that you are suppose to pull a fuse for 30 seconds to clear all codes??? Hoping this new sensor will help me, I am getting around 12-15 mpg

 

Also, I checked ohms across purple and white, and its reading 10.

 

(10 is close enough to 7; I doubt your meter is any more accurate than that)

The code 21 is (basically) telling you that the ECM sees an open or short on the heater circuit. Since you seem to have identified the correct wires on the sensor, do you have the correct wires on the truck? If so, are they connected back to the ECM? You can test that quickly by looking for 12v on White/Red, and continuity to ground on Green/Black. Then to see if you have excess resistance (nearly broken wire?), hook up the sensor and see if you get the same voltages while the heater is pulling current.

Last but not least, are your splices any good? Using those hardware-store crushable jobs is beyond my skill level.

Good luck.

 

OK.... I guess I do not know what I am doing. I have 12v across w/ red and black on the truck. When I crank it up, I have anywhere from 12 to 13.5 when the new sensor is hooked up. Still getting code 21. I have it hooked up like this:

Truck- new sensor

w/red- white
w/green- purple
brown- grey
black- black

 

Question. You are clearing the computer with a code reader or scan tool thru the OBDII connector, correct?

 

Oops sorry brain froze, forget the above. Wrong year

 

OK. So I changed the ECU and got a toyota O2 sensor, and that cleared all codes. Now, it runs great goin down the road, even seems to have alittle more power, problem now is it idles rough, Any thoughts??