[OzzyWJ]

just been searchin round on the net and here but cant find it exactly what i need. Testing the o2 signal wires on my wj v8 and all 4 wires are showing 1.5volts give or take .10 volts. This is while the ignition is turned on only and either plugged into the o2 sensor or not the pcm is showing 1.5 volts along the signal wire. Is this normal or do i have a serious problem.
I have had 2 codes pop up now of 0132 and 0138 bank 1 both o2 sensors are reading high but both bank 2 o2 sensors are still ok but all are showing this 1.5 volt.
Because i have read on numerous pages that at the signal wire with the ignition on it should read about .45 volts.

[greasefingers]

The sensors upstream (before the Cat) are important for controlling the air-to fuel ratio. They help determine the duration of time that the injectors stay open. The O2 sensor has two circuits. The sensing and heating circuits. It cannot yield accurate output voltages unless it is around 700 degrees F, so a separate heater is built into the sensor. This also helps the engine enter the Closed Loop method of control sooner.

The output of the measuring circuit is more difficult. With a hot engine one can back-probe the connector. The voltage output is a Sine-wave. So if you connect a voltmeter across the correct pins, then the meter will constantly bounce back & forth between 0.1 & 0.9 volts. A good sensor will bounce between a much narrower range like (0.25 to 0.75). The important thing is that the average of the swing equals 0.45 volts. Measuring this output is tricky as it changes constantly and receptively with time and is better to use a voltmeter with an averaging function. (only the really cool & expensive ones have this)

You can easily test the heater circuit if you know which two wires to measure. With the engine cold and off unplug the O2 sensor connector. Check for resistance on the sensor side. An Open circuit or mega-ohms means a bad heater circuit. Throw the O2 sensor in the trash.

[rm2001wj]

When measuring O2 sensor signal voltages, the engine must be running and the heated O2 sensor must be at it's normal operating temperature. Just turning on the ignition is not sufficient unless you just want to measure the heater voltage (about 12V between the heater wires). Normally with the engine off but ignition on, the signal voltage from the O2 sensor is very near zero; not 0.45V.

If it's not a mistake, 1.5V on the signal wire coming from the PCM might indicate a problem. With the engine running and O2 sensor hot, the only voltage on the signal wire should be that generated by the O2 sensor. As mentioned above the signal voltage from a good sensor should vary between about 0.2V and 0.7V which would put the average at about 0.45V, but the engine must be running and the sensor hot for this to occur.

Try measuring the signal voltage under running conditions, and it will take several minutes of running for the sensor to get hot.

EDIT: This web page might be useful to you:
http://www.aa1car.com/library/o2sensor.htm

[OzzyWJ]

will try that with it all warmed up. also was thinking would the pcm put out a voltage to the sensor while it is cold since the pcm doesnt read fron the o2 sensors till it is at the right temperature. just somthing i thought abouyt b4 since all 4 signal wires have the 1.5 volt reading but only 2 codes. so 2 are working corectly and 2 arent. will do some more probing around and will swap sensors around too might end up being a bad connection since this car was submerged a while

[greasefingers]

The PCM only provides 12v to the heater circuit and not the sensing/measuring circuit. It also reads the output voltage from the sensor. The output from the senor provides its own power thru a chemical reaction.

[OzzyWJ]

I have had a play around with the sensors and swapped the bank 1 sensor 1with bank 1 sensor 2 and i am not getting a code for the front o2 sensors but i am getting it for the rear 2 o2 sensors now codes 138 and 158. so i am getting some where. either there is bad connection probs on these 2 plugs which is what i will be testing for next or these 2 o2 sensors have turned faulty.

[rm2001wj]

Keep giving progress reports.

[greasefingers]

Oxygen sensors are the most prone sensor to take a dump on any vehicle made. This is because they are in a ridiculous environment (heat and nasty gases).

You need to replace the O2 since it has been moved to a new location and the error code changed and followed the sensor. This would be the most logical thing to do.

[OzzyWJ]

hey have put new connectors on these rear o2 sensors and yeah ends up being they are done for. so i have put the old ones back in for the hope they might still work till i get these other ones sent back for exchange. Well at least my 2 front ones are working a treat. Just a thing about the fuel filter does this hold the regulator inside it. If so if i replace this it may fix my starting problem. if it doesnt the fuel pump may need changing aswell then. cheers fellas

[rm2001wj]

Yes, filter and regulator are combined into a single unit.

[OzzyWJ]

sweet thanks for this. will change the filter and see if this fixes my starting problem. have been driving around all day with my old o2 sensors in with no problem so this must mean my wiring is ok. will send the new ones back.