02 wiring/circuit check

'93 xj manual trans. I cleared the code on my ECU and without starting the engine i check the codes and got 02 sensor code. Is it safe to assume that it is a wiring problem? maybe the ECU is bad? i've replaced the 02 sensor already. whats a good way to check the circuit and wiring for it? I've already replaced the 02 sensor with an OEM sensor

You may have 2 sensors, 1 on the cat 1 on the front down pipe, did you change them both?.............

There's only one. nothing else after the down pipe or after the catalitic converter. do the wires from the 02 sensor cross or splice with any other wires?

rooster87 said:

There's only one. nothing else after the down pipe or after the catalitic converter. do the wires from the 02 sensor cross or splice with any other wires?

Click to expand...

Have tried starting and running it to see if the code goes away?

There is an O2 heater relay that preheats the O2 sensor. But once the engine is hot and the O2 sensor is hot the O2 sensor should start working even if the O2 heater relay is bad.

Ecomike said:

Have tried starting and running it to see if the code goes away?

There is an O2 heater relay that preheats the O2 sensor. But once the engine is hot and the O2 sensor is hot the O2 sensor should start working even if the O2 heater relay is bad.

Click to expand...

Interesting. i didn't even know there was a heater. the reason i ask if there's a splice is because i tried earlier to trace the wires from the 02 sensor to the ECU, found that the green/black wire and the brown/black wire are connected somewhere. Used my multi meter where it beebs when there's a closed circuit (beebs when the probes touch eachother) and it beebs when i put the probes on those 2 wires. I need to get it on the road it's my DD.

Oh and I HAVE ran it before. The CHECK ENGINE light comes on.

rooster87 said:

Interesting. i didn't even know there was a heater. the reason i ask if there's a splice is because i tried earlier to trace the wires from the 02 sensor to the ECU, found that the green/black wire and the brown/black wire are connected somewhere. Used my multi meter where it beebs when there's a closed circuit (beebs when the probes touch eachother) and it beebs when i put the probes on those 2 wires. I need to get it on the road it's my DD.

Oh and I HAVE ran it before. The CHECK ENGINE light comes on.

Click to expand...

That just means you do not have an open circuit, which is good news, but does not tell you much more. The resistance between those two wires should be pretty low as the O2 sensor generates a very low variable volatage, <1.0 V, signal to the ECU. You are reading the resistance of the wires and the ECU circuit (plus the O2 sensor if it was still hooked up).

Have you checked the O2 sensor wiring near the exhaust manifold, it is real easy for that wiring to have an unfortunate encounter and get burned and grounded down there (happened to me shortly after replacing the O2 sensor when the wiring shifted, I had to repair the wiring harness/connector and since tied it out of the way of the exhust pipe.

Check the third wire going to the O2 sensor for something like 12 volts when you first turn the power on (don't start it). If there is no voltage, it may be the O2 heater relay, I am not sure of this, but I think I recall reading that no volatge to the O2 heater would throw an O2 sensor code.

Hear is a link to the Meter testing of the O2 sensor:

http://www.naxja.org/forum/showthread.php?t=905705

And another:

http://www.naxja.org/forum/showthread.php?t=66704&page=2&pp=15

On my '91 it was a ground wire connected to the block behind where the oil dipstick tube bolt. I wasn't getting a check engine light though just a soft code that was stored and would show when doing a check. HTH.