I just tested the O2 sensor on my 240 and I got 0 omh and 2 volts after the "closed loop" cycle at idle and with the RPM's up a bit I got 0 ohm and 13-15 volts. Sounds like I need to get a new sensor, right?
The reson for testing it was for failing the emissions without even breaking a sweat.
--
88 240DL a.k.a The Blue Tank

I am not aware of any test for the O2 sensor that involves using an ohmmeter. The O2 sensor generates a voltage based on the presence or absence of oxygen in the exhaust stream. This voltage will shift back and forth from below to above 0.5 Volts. e.g. 0.1 Volt to 0.9 volts. The low voltage is lean, O2 present, and the high volage is rich, shortage of O2 in the exhaust. There are good descriptions of how to test this sensor located in previous posts (earlier this month if I remember correctly) and in the FAQ I believe. For any testing of the O2 sensor, it is necessary to get the engine up to normal operating temperature. This is also important for your emission test - It is usually advised to take a 20+ minute ride before going to the test station.

Was the emission test static test or dynomometer test? Generally high CO or HC would indicate a rich condition and high NOx would indicate a lean condition. If all three are out of range, it could indicate an engine miss.

Please post your test results and the limits.
Other helpfull information:
Model year.
Milage.
How does the engine run - how many miles per gallon.
Last time plugs, wires, cap, rotor, and air filter were replaced.
When was the flame trap last cleaned and oil changed.

Post back with the above info and the board will be able to provide some very useful help.

Dan

I had talk about the emission in a previous post I will paste it on this post. Its is a 88 DL with around 97,000 miles.

I went to get it the emissions inspection and it faied it, so I am stuck with no car until it passes. I would like to do must, if not all, the work my self. I
am very good at repairing cars. The only thing I did before the
inspection was put new spark plugs(wires, cap, roter were replaced
last year and r n good shape) and air filter and put some STP in
it. The car was setting 4 almost a year but was crank a lest once a
year and I drained out must of that old gas.
After the inspetion I found some broken vacum hoses and have replaced
them and changed the oil. Is this enough or do I need to do more? And
y did the NOx pass on the 2nd and not the 1st?

Emission Result
25/25 Test
Reading Allowed
HC ppm 383 162
CO% 2.9 1.04
NOx pmm 1358 1163
50/15 Test
HC ppm 423 167
CO% 3.67 0.94
NOx pmm 1059 1273

Thanks,
Ace

NOx is an indicator of lean condition or excessive operating temperature. If your timing is too far advanced, this will cause excessive temperature. Go back and look for more air leaks as this is also a primary cause. Don't rule out your catalytic converter. Don't jump the gun and change it needlessly either. Make sure everything else is in order first.

Dan

Retest your O2 sensor properly like dan52 suggested. Your readings make no sense. And don't use STP in any vehicle you intend to keep.