hey i just put in a new o2 sensor into my 94 lx. if i let the car sit for an hhour or two, when i start it the cel comes on. but if i turn off the car and turn it back on the light goes away. any ideas on how to fix this?

 

Read the error code & come back to tell us what that says.

 

its error code 41, heating circuit malcfuntion on the o2 sensor. its a brand new oem sensor. if i start the car the error is there. turn it off and back on, its gone

 

You need to be sure the heater voltage is available with the key on.
Try this link;
http://img139.imageshack.us/img139/3...acode41no7.jpg

 

could this be caused by the grounds being switched?

 

Switched??
If you move a ground to a different location, but it's still a good ground, I don't think that would be a problem.

If you move it to someplace that isn't such a good solid ground, or if you leave it hanging (forget to bolt it down anywhere) that could be it.

 

sorry, let me re-phrase. is there some sort of mis-wiring in the o2 sensor itself that could cause this?

 

Is it a generic sensor where you had to splice the wires into your old sensor's plug?

There's 4 wires. Signal (+), signal (-), and 2 heater wires. The 2 heater wires can interchange with each other (it's a simple resistive heater). But the signal wires have to be correct.

If one of the signal wires is connected where the heater should be, that'll certainly cause code 41. But it should also cause code 1 because the signal won't work either.

Another thing that might cause code 41, is either one of the heater wires touching ground. They both should be insulated properly, & that entire heater circuit isn't supposed to be grounded outside of the ECU.

 

it had the plug already on it. how do i check if its grounded?

 

Unplug the sensor. Find the 2 same-color (black?) wires going to the sensor itself. Get your multi-meter & set it for resistance (ohms). Measure between those 2 wires - it should be 10 - 40 ohms.

Then measure from each one of the wires to a good ground. This time it should read Open-Circuit. (Or the same thing your meter says when the probes aren't touching anything.)

A similar check of the circuit in the car's wiring harness is more complicated. You can test the 2 corresponding wires in the plug. When the key is turned OFF, I'm not sure if the ground side of that circuit is actually connected through the ECU. I'm tempted to say the test is the same, but I'm not sure how that behaves when the ECU is not powered up.