All of the wires get contaminated at the harness connector junction. There are some people running a separate ground wire and getting results, but I would not recommend this approach for two reasons: 1) you leave the O2 sensor wire in the harness with the power and ground wires for the heater, which it can also short to and ruin the sensor/degrade the signal. 2) the O2 sensor ground is not a ground in the sense of most other components. It is an isolated ground from the PCM that all sensors utilize. Grounding sensors directly to the vehicle chassis is grounding them to the same ground as the ignition coils
, starter, and other electrically "noisy" components which can result in a bad signal to the PCM, which will create all the same problems as before. This may not occur immediately, or may never occur, but simply "re-grounding" the O2 sensor is not a good idea for a permanent solution.
You can replace the pins in the connector, but this still does not remove the ps fluid still coating all of the wires. While this may remove the immediate cause of the problem, the O2 connector is still the low point on this wiring harness, and eventually will again become the collection point for residual fluid in the harness. I can imagine this is why Dodge created a "bypass harness" since they realized that it was the best thing short of removing the entire wiring harness and cleaning the wires with de-greaser. (a viable option if you are that determined
), or replacing the whole harness - $$. Unfortunately, it appears that most Dodge "techs" are ignorant of how to install it, since it only occured on one model vehicle, in one model year.
I sucessfully finished repairing mine yesterday after 1.5 years of screwing with it, researching it, and letting my Durango sit in the yard (could not get it registered with engine light on)
If you look at an engine wiring diagram (hayes, chilton, etc.) it shows the four wires to the O2 sensor. There is 12V for the heater, a "chassis-ground" for the heater, a signal wire from the sensor, and a "PCM-ground" for the sensor. (I am making up the ground terms to keep them separate, do not look for them in the manual) . I left the sensor connected to the heater and heater ground, since I had proper voltage there, and the heater circuit fuse has not blown. The heater circuit can handle a lot more contamination than the sensor circuit since it can just "burn" through it, so I have left it intact for now since it is not part of the problem.
I ran two new wires from the sensor, the signal and "PCM" ground wires, up to where the PCM is mounted on top of the right fenderwell in the engine compartment. (the black 'signal' and gray 'ground' wire if you are using a Bosch universal replacement) From there I opened the main harness leading into the PCM and located the wires. The signal is a light green with red stripe,(note there are two wires this color, one is O2, one is transmission, I used trial and error) and the "PCM isolated ground" is black with a blue stripe. The signal wire must be cut, and the new wire from the sensor connected to the end going into the PCM. If you do not cut it, but rather spice it, you have essentially left your sensor connected to the point of contamination that you are trying to avoid. The ground wire must be spliced into the one in the harness bundle so as not to disconnect other devices using the same ground. I used an automotive crimp style spice sold at auto stores.
So far I have driven 70 miles with no problems. I have a scanner, and both oxygen sensors
are reading fine. The front sensor switches from
0.080 volts to
0.810 volts at a regular interval. The system is running in closed loop mode like it should, and there is no engine light.
I understand this may be somewhat vague if you are not somewhat handy with automotive wiring, but this post is half a novel already so I will leave it at this for now to see what areas are clear and which are not so they can be answered in future posts. If I get the time I would like to put the whole procedure on a webpage with pictures since Dodge is not really helping anyone and this is the only place on the entire web that is.