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So, this truck is throwing engine code 27. That's the code for O2 sensors for a california emissions truck (according to the haynes manual). I've replaced both O2 sensors and it's still throwing a code.
Now, I think it may be the wiring on the rear sensor. Before I bought the truck, someone hooked up an aftermarket muffler shop exhaust system that, in my opinion, isn't very good. The rear O2 sensor is one of those universal ones that needs to be spliced. Whoever hooked up this one spliced it BEFORE the connector! So, there's no connector to hook up the sensor that was designed for this truck. The point is, I think the way it was wired up is bad.
Any thoughts? I'm not sure which wire is which. I wouldn't mind just replacing the entire wiring harness, but that's a $900 part, and who knows how long it would take. What else could it be?
Code 27 is the sub-O2 sensor, the one behind the converter. It has two possible meanings- the main O2 sensor is reading rich and the sub sensor is reading lean, or there is a problem with the heater circuit on the sub-O2 sensor.
Don't quote me 100% on this but I believe the wires should be:
white/red and brown wires: heater circuit. white/red should have +12v, brown is ground.
white and red/green: wires to the ECU.
The O2 sensor should have 2 black and 2 white wires. The white wires are the heater circuit and the black wires are the O2 output.
right now i have it wired like this (O2/Wiring harness):
Black to White
Black to White/Red
Blue to Red
White to Brown
How should it be wired? I only did it this way because that's how the last O2 sensor was wired up, but maybe that's not right. I have the feeling the dealer did it like that just to get it fixed to sell it.
i was going to look under mine, but its not cali emissions, and its a 22r, so I dont think it would have worked anyway! I think I only have one sensor before the cat!
...white/red and brown wires: heater circuit. white/red should have +12v, brown is ground.
white and red/green: wires to the ECU.
Originally Posted by OltorfTD
Ok, here's what I got:
O2 sensor: 2 black wires (heater wires, i thought) 1 white and 1 blue wire
Wiring harness: 1 white, 1 white/red stripe, 1 red, 1 brown.
right now i have it wired like this (O2/Wiring harness):
Black to White
Black to White/Red
Blue to Red
White to Brown
O2 black to truck's white/red, O2 black to brown. < heater circuit
O2 white to truck's white, O2 blue to truck's red. < O2 signal circuit (I bet if you looked hard, you'd see a green stripe on the red wire.)
If that doesn't help, you might need to reverse the O2's white and blue leads:
O2 blue on the truck white, and the O2 white on the truck red (red/green).
Ok, I got ahold of a wiring diagram and I figured out which wire was which. The sensor's 2 black wires go to the truck's red/white and red/green wires. The brown wire is the ground wire and goes to the sensor's white wire. The truck's white wire is the signal wire and it connects to the sensor's blue wire like this:
Truck: sensor
White: blue
Brown: white
White/Red: black
Red/green: black
If you're curious, the brown wire connects to a few other brown wires and grounds. The red/green goes to the heater control in the ECU. The white/red goes to engine sensors and (i think) determines when the temperature is cold enough to turn on the heater. The white is the O2 signal wire and sends the O2 info to the ECU.
The light is off now, so i'm pretty sure it's working right. I drove it around for 15 minutes or so and it didn't come back. If it does come back, I'll post up, and we'll know this way is wrong.
i was going to look under mine, but its not cali emissions, and its a 22r, so I dont think it would have worked anyway! I think I only have one sensor before the cat!
I have the 22re and could use your infor on the wiring colors if u still have it can’t get my engine light off have replaced the 02 sensors and the ecu
Ya know, you're responding to a post by 1989toy4wd, but he has not posted here for ... 10 years. He might still be around, but somehow I doubt it.
Why don't you just post your question. What make/model/year/engine/transmission/body are we talking about? What code(s) do you have? Have you done anything besides replace two O2 sensors and an ECM?
Ya know, you're responding to a post by 1989toy4wd, but he has not posted here for ... 10 years. He might still be around, but somehow I doubt it.
Why don't you just post your question. What make/model/year/engine/transmission/body are we talking about? What code(s) do you have? Have you done anything besides replace two O2 sensors and an ECM?
my truck 89 Toyota 2wD , 2.4 l fuel injection, code 27 come and stay for 3 years I try 10 sensor 7 ecm and light still on , I check all parameters and light still on and obviously no pass smog truck is California emisión , and last ECM from cardone is the only one with 90 % customer satisfaction is the 22 re only one the truck runs almost perfect, but I’m searching because the light still is on it doesn’t matter what I try , I’m in Las Vegas nevada
05-30-2009, 04:24 PM
