I am trying to figure out the wiring harness for my 2002 LQ4. I have what seems like two different connectors for the front and rear o2's. In my ignorance i have acquired 6 o2 sensors, 2 of one type and 4 of another but none of them fit on my harness, is it possible to just change the connector? where would i get it? since i will have the rears tuned out what o2's would connect to the front connectors? FYI my PCM is red and blue
thanks

the fronts look like this (I assume that is what these connectors are for)
http://i413.photobucket.com/albums/p...Picture006.jpg
and the rears look like this
http://i413.photobucket.com/albums/p...Picture014.jpg

I got these ones on the engine, oddly the harness which was fully connected has no matching connector.
http://i413.photobucket.com/albums/p...Picture001.jpg

then i went back to the yard and got 4 of these
http://i413.photobucket.com/albums/p...Picture005.jpg

 

With the red and blue PCM you should be using black 02 connectors. I cannot open your photos (my network wont let me). The reason GM put different connectors was to prevent hooking up the O2 to the wrong spot (eg hooking Bank1 Sensor 1 O2 Sensor to Bank 1 Sensor 2 connector).

 

do you mean the harness side is black or the sensore side? the back connectors are square and the front are flat (4 pins in line).
thanks

 

Both sides, the sensor and the harness connectors will be the same color. If you have four flats, those are the same as the early LT1 sensors. The triangular and white O2s are the wrong ones. Dont use them. P/N for the Flat sensors are 25312184, square blacks are 25312201, both are gm numbers. They can be cross referenced.

 

thanks for the replies and part numbers juced211s, that is exactly what i needed. now if i could find someone to trade the 6 i don't need for 2 that would work, i guess i will try some yards. I also found some info about halfway down the link bellow
http://chevythunder.com/ls1_page_1.htm

 

PM sent. -Bob

 

For anyone who is interested, www.lt1swap.com has a page that describes the various LS sensors, mostly 5.3 and 6.0 truck sensors. Even has pictures.

 

is there more than one type of the flat black connector type?

thanks

 

No there is only one flat black O2.

 

juced 211s
why cant you use the triangled sensors?,because i have that style connector on my harness.
thanks for any info!

 

There is a male and female version of each connector making 6 styles of HO2

I havent run across any of the newer triangle ones so the tally may be 7 or 8

 

You may be able to use the triangle style, those I am not sure about. If they were used in a red/blue PCM they will work. Would like to know for posterity.

 

I was under a 2006 Silverado 5.3 yesterday and it had the triangular plugs. I remember because the wires had wrapped around the front driveshaft and pulled out of the plug on the harness side.

 

Well the 06 is a green/blue pcm so would be interested to know if they used those on the early PCMs.

 

So are all the sensors the same, just with different connectors? If they are, it seems like you could:

1) Buy just the sensor with no plug on it, and put the plug on that matches your wiring harness, or
2) Find a used 02 sensor, cut off the plug, and put one on to match your wiring harness (or you could change the plug on your harness to match the sensor)

I like option #1 the best. You can find Delphi universal O2 sensors for about $20. (Not sure if they're the same as AC Delco/Denso) I wouldn't mind splicing plugs on to save $20 per sensor.

So are all the GenIII 02 sensors the same? How about the GenIV sensors? Every one I have come by has 4 wires...

 

from what i understand, the black sensors are grounded to the exhaust and the white sensors ground back to the PCM, so you cannot mix across colors (I am not racist, GM is).

P.S. I have 2 of the triangular white ones that I don't need

 

Jet black is correct. You cannot just cut connectors and use what you have. You have to make sure that you use what is compatible with your PCM.

 

yes my harness is a 02 6.0 harness with red/blue connectors.front o2s are tiangular,rear o2s are square,dont remember if they are white or black?

 

If that is the case then the triangular ones you have are good for any red/blue setup. You could swap in black square or flat black 02s and they would work on swap connectors.

LS, Thanks for the info on that!

 

I think any of the o2 sensors would work with any of the harnesses (99-02) if they are wired correctly.

GM used CASE grounded o2 sensors and ISOLATED Ground O2 sensors. The CASE Ground type are only found on SOME 99-02 models.

After 2003, all o2 sensors were isolated ground. GM stopped referring to them as such, because all had changed, and there were no longer two types. for 2003+ applications, I would recommend running the o2 sensor designed for the harness, since the PCM now controls the heater circuit, using older sensors in this arrangement could cause issues.

In case grounded O2's. The TAN wire or TAN/White is connected to the BODY of the o2 sensor, where it threads into the exhaust pipe. There has to be a good ground from the o2, to the exhaust pipe, to manifold, to cylinder head. the PCM uses this as the GROUND reference when reading the O2 sensor SIGNAL on the purple wire. Each oxygen sensor has its own tan or tan/white wire going directly to the PCM. (PCM Blue pins 25,26,28,29) US and Mexico built trucks used this type, and the 5.3's Had flat front o2 sensor connectors.

In isolated ground o2's, the TAN wire from all 4 o2 sensors IS NOT connected to body of the sensor, and all 4 wires go into a splice pack in the harness. Then 5 wires come out of the splice and go to the PCM. 4 of the tans go to the SAME place as above in the case ground type. Then an additional TAN wire goes into the PCM (Blue Pin 63) to a Ground Reference provided by the PCM. this way, the PCM is supplying the ground reference to all 4 o2 sensors, which will be much more reliable then case ground type. Canada built vehicles got this type.

Okay, in 2003, all o2's were now isolated ground type. A change was done INSIDE the PCM so that the splice pack, and the 5th TAN wire to the PCM was not needed anymore. Each of the 4 locations in the PCM for the o2 senor tan wire, is now a Low Reference.

You need to first figure out WHICH TYPE of sensor you have. CASE or ISOLATED Ground. Check for continuity from body of the o2 sensor to the tan wire. Keep in mind, most o2 sensors wires are not color coded same as the engine harness, find where the tan wire WOULD go, and check it to the body of the sensor. This should be done with sensor removed from vehicle, and unplugged from harness, to avoid any incorrect readings. If you get continuity you have the case ground type, if NOT then its isolated.

Next, figure out what type of harness you have. inplug the PCM blue connector, and all oxygen sensors. Check for continuity from tan of one sensor connector to tan of another. If you get continuity, then there is a splice pack on the tan wires, and you have a ISOLATED ground harness.

For an ISOLATED ground sensor to work in a CASE ground harness, you will have to tie all the TAN wires in the engine harness o2 connectors together to a common ground point, could be to engine block, would probably work fine.

I'm pretty sure a CASE ground sensor would work fine in a ISOLATED ground harness without any modifications (other then o2 plug of course). In this arrangement, the o2 sensor would be getting a Ground from the body of the sensor, AND the splice pack in the harness.

The triangle connector o2's I've only seen on the FRONT set, on 6.0L/8.1L engines. 01 and 02 model year, the PCM supplies GROUND to the oxygen sensor heater circuit on the FRONT o2 sensors only. I think this is why GM used a different sensor, is to keep them from getting mixed up. The PCM modulates the ground to control heater current. I'm not sure, but I think you'd have problems with the heaters if you wired the heater in this directly to ground/power. I would not try to use a triangle plug sensor for a substitute someplace else. These harnesses also had a mix of CASE ground and ISOLATE ground sensors in the SAME harness. The front o2's were isolate, with the after CAT's still being a CASE ground. Now this was not 100%, you could have a mix of both types, or all one type. very confusing when you get into the 6.0 and 8.1 o2 wiring.

LS1 F-Body all used CASE ground, up to 02. These used the sensors with female pins, black square plastic connector.