1994 pickup cali emissions? code 27
 

Hey guys,
I'm having a problem with my 1994 22re pickup. The ECU is throwing a code 27, which I've learned is the sub-oxygen sensor - the sensor before the cat. I installed a new bosch OE style sensor to no avail, cleared the ECU and after about .5 seconds of running the code is back. Looked around some more for wiring/connection problems and found an extra set of wires for another oxygen sensor. They've been cut and have nothing connected to the connector on the end. I'm thinking maybe I have a cali emissions vehicle with after market exhaust, although it certainly looks like a standard exhaust system. Would a non-cali vehicle still come with the wiring for the second sensor? If it is cali, do I have to weld a new bracket for the second sensor in after the cat or can I trick the ECU somehow?
Thanks in advance guys,
MJK

Yep, 2nd O2 sensor after the cat. That is what the ECU uses to check on the cat. convertor condition and makes sure it is working OK. A muffler shop should be able to weld on a new bung for the 2nd sensor or pick up the cat-back piping from a similar vehicle in a junkyard.

Also, Denso is a better sensor for a Toyota, Bosch seem to cause problems for many folks on Toyota engines.

Yeah denso is definitely the way to go. I got my 02 sensor for around 40-50 shipped and works perfectly.

Not sure if it will work or not but im thinking you could swap the ecu with a non cali and be good. Im sure someone can chime in and correct me if im wrong

Thanks guys! I have a spare system I will probably cut out the section of pipe with the bung in it and weld it in after the cat. Would there be any harm in hooking up a sensor beforehand to see if the cel clears?
Hopefully getting this fixed will improve my crappy mpg! (14 city and I drive like a grandma!)
Thanks again,
MJK

How do I go through the pinpoint checks for this code? I am not sure if it is my rear sensor or not and it is so rusted that I highly doubt I will be able to get the rear O2 sensor off? Any advice would be lovely. Thanks

Simple check would be to measure the resistance of the heater circuit for that sensor:
- http://www.4crawler.com/4x4/O2SensorWireColors.html