The O2 sensor is very sensitive to excessive circuit loads and circuit damage of any kind. For safest testing, disconnect the O2 sensor connector, install jumper wires to the 2 connectors and connect your voltage meter to the jumper wires. If jumpers aren't available , carefully back probe the wires in the connector shell with suitable probes (such as T-pins). Do not puncture the O2 sensor wires or try to back probe the sensor itself. Use only a digital multimeter to test an O2 sensor.

Note: Performing the following test will set a diagnostic trouble code and illuminate the Check Engine Light. Clear the diagnostic trouble code after performing the test and making the necessary repairs.


Voltmeter + lead to terminal #2 and connect the - lead to terminal #1 at the O2 sensor connector. If testing a single-wire O2 sensor, connect the - lead to a good chasis ground. turn the ignition key to on but do not start the engine. The meter should read approximately .40-.45 volts. If it doesn't, trace and repair the circuit from the sensor to the PCM.



These test should be performed with the engine at normal operating temps.

a) The voltage from an upstream sensor should range from 100 to 900 millivolts (0.1-.9 volts) and switch actively between high and low readings.

b) Voltage from a downstream sensor should also read the same but it should not switch actively. The downstream oxygen sensor voltage may stay toward the center of its range (about .4 volts) or stay for relatively longer periods of time at the upper or lower limits of the range.

Check the battery voltage supply and ground circuits to the O2 sensor heater. Disconnect the electrical connector and connect the voltmeter -lead to terminal 3 and the +lead to terminal 4 of the sensor connector. Turn the Ignition to On. The meter should read approximately 12 volts. If battery voltage is not present, check the power and ground circuits to the sensor (Don't forget to check the fuses first).

Allow the O2 sensor to cool and check the resistance of the O2 heater. With the connector disconnected, connect an Ohmmeter to the 2 O2 heater terminals of the connector(Oxygen senor side). The O2 sensor pigtail is generally not color coded, but the heater wires are usually the white ones. The O2 sensor heater resistance should be 3.0 to 10.0 ohms. If an open circuit or excessive resistance is indicated, replace the O2 sensor. Note: If the test indicate that the sensor is good, and not the cause of a driveability problem or diagnostic trouble code, check the wiring harness and connectors between the sensor and the PCM for an open or short circuit. If no problems are found, have the vehicle checked by a dealer service department.




Per Haynes Manual

 

thanks montyss!

 

thats alot of crud to go through, ./.....just remove the entire exhaust system, ;p just playin./ anyways i got a new ignition control module from pick and pull, it was 13 dollars and i took it straight to autozone to get it texted, its located under the ignition coils(its actually what they are bolted to.) siz small bolds and three nuts(undernieth) unless monte, then its two torque bolds runing into the engine. car seems to run fine now, i havent done anthing to it since it threw the codes, service light went away(ill see how long that lasts) . dont replace the sensor or cat till you know thats it, cause it its not the outlieing problem than you just waisted money on a cat which is trashed cause its still doing the same thing. make sense? this car will be the death of me,. but i love it////// btw the engine thats in them won top 10 best engine 3 years in a row

 

i already replaced the thing under the coils.

 

i ran some seafoam throught the vaccum lines and egr valve, then added the rest through the tank, pressure tested the fuel rail , all is good there. i have yet to see a check engine code, no loss of power,. seems to have solved the problem. if i were you i would change an o2 sensor then your cat.