rentedmule

Hey everyone, sorry if this topic has already been addressed, I'm a newby. I changed the exhaust on my 93 3.0l 4runner and I'm getting an O2 sensor code when I short the diagnostic leads. The shop had to use a torch to get the sensor out of the old exhaust so I changed out the sensor for a universal NTK one (the same one that I had on previously with no prob) and still couldn't clear the code (by pulling the EFI fuse). I then put a new high flow catalytic convertor on, thinking that removing the cat when i changed the exhaust may have caused the problem but the code still will not clear. I'm running out of patience and $$$, anyone have any ideas?? Will having the code read with an actual OBD1 diagnostic computer tell me anything more than shorting the leads? thanks alot

suprathepeg

Check for a short in the wires from the O2 to the ECU.

Toysrme

What exact code is it.

rentedmule

If I remember correctly the code that was showing up was a 21. thanks for the input!

Bassinfool

That's the exact fix I had with my code 21. The wire just above the O2 was fried. Quick splice job & no more problem.

Toysrme

Ya Code 21. For us cars, that means the rear bank, rear = right hand = odd bank.

With the truck cold, plug a multi-meter into the o2 wire so you can read the voltage output.
Crank the car & immediately start driving around. It should take about 30-45 seconds for it to come up to temp. They can take up to 2 min idling, and sometimes never come up to temp. If it doesn't come up to temp- the sensor is lazy & has poor responce time.

Also, when it has reached temp, watch the output of the o2 sensor. It should be bouncing between 0.4 & 0.55 volts. The ECU will throw 21 if it stays below .4 volts over 1500rpm & go into open-loop mode. (The lower the voltage, the leaner.)

Under either of those conditions, the thing is toast - replace it with a $30 generic splice in o2 sensor & for that cheap, ya might as well do both!

Most of the time, Toyota did not use a heater circuit on their main o2 sensors on OBD-I. They did on cars equipped with a post-cat o2 sensor. If the 3vz-e broke that trend & has headed main o2 sensors - the generic Toyota spec is 11-17ohm when you disconnect the o2 harness & check resistance across HT & B+.






Tho it does go against "obvious" troubleshooting B/C only one bank has a proven sending a lean code - check for vacuum leaks after you replace the o2 sensor. Toyota OBD-I is notorious for letting problems slide, and hell WILL freeze over before OBD-I Toyota throws a lean, or rich code most of the time.

highway74

My o2 sensor's gasket rotted out which I was totally unaware of and as I was driving down the highway, guess what worked its way out? You wanna talk about loud. I thought the pipe had rotted again, but it was just that nuts had backed themselves off due to vibration. It never threw a code even dangling in mid air hanging by the wires. I bought a new sensor, since it was off already, cleaned up the rusty threads with a die and I was done. I figured after 12 years it was time.