Hey all. I went to install new (all 4) 02 sensors on a friends 2001 Durango 4X4 with 360/auto. Got 3 of them on but can't get to the plug connector on the upstream/drivers side location... no way, no how . It's sandwiched between the top of the trans and the body. Can I just cut the plugs off the new/old sensors and splice together? Or is a universal sensor needed. These are NGK sensors btw. Thanks Moparts

It's possible, I got to the one on my Dakota. That engineer should be pimp slapped. You need a degree in contorsionism, and a massive amount of patience. But if that fails, you can splice them. I can't remember how mine actually came apart, but when it did it was a surprise that it did.

Splicing wiring on an o2 sensor is not a good idea.You can get at the sensor if you drop the trans crossmember and lower the trans.I know it is a lot of work but can be done.

Just went through this on my own '01 Durango R/T (5.9, auto also). That harness connector was a total pain to get to. Considered what you're thinking of doing, but didn't want to commit and then find that I couldn't get a soldering iron on the wire(s), or whatever. After enough dorking around with it and a few breaks to calm down, finally got the connector off. Luckily, the harness part that gets mangled while prying them apart is the part that stays with the sensor.

Didn't have a sensor socket, but luckily the sensor hex is big enough that an open end wrench (and a lot of PB Blaster and elbow grease) did the trick.

Good luck.

Mopar does not like you to solder the 02 connector wires unless its up above the connector in the harness side by about at least an inch or more. The 02 sensor actually draws a small amout of outside air thru the wires to compare it to the air (02) in the exhaust. It does that right at the connector so if you go a good inch or more above it the sensor should still work as long as you have a good clean solder and its good to use the heat shrink with the sealer in it as that seals up real good.
Also on mopars from about 2000 and newer the downstream 02 does more then just give the PCM a reading to compare to the upstream 02 and see how the converter is working. It also uses the downstream 02 sensor reading to set the goal of the upstream 02 sensor. The goal is the switching point from lean to rich which is normaqlly .5 volts but if the PCM sees the downstream 02 hanging say more rich then it should it can change the upstreams switching point (goal) as if it sees it rich to long it will drive the goal to a slightly lower voltage an moniter it to see how it does after that. In other words the 02 normally has to go just below .5 to switch from rich to lean but if it drives the goal down to about say .4 volts then the PCM will be driving the fuel mixture lean longer as its above .5 it sees rich and is driving the fuel lean and with the lower goal it wont switch back at .5 but will keep driving it lean until the volts drops to .4 and that will help if its seeing to rich a reading for to long. The same goes if it sees to lean as it will raise the voltage some. It also takes into account the adaptive fuel cells its in.
Also somewhere around 2005 or so Mopar changed the 02 voltage readings as the raised the voltage reading to read from 2.5 to 3.5. They did this by biasing 2.5 volts on the ground side. It gives less chance of small resistance causing voltage problems and bad readings. You just have to remember on the ones like that the 02 just reads from 2.5 to 3.5 instead of 0 to 1 volt. Ron

i agree with 383man that some O2 sensors do the odd thing of "breathing" through the tiny space between insulation and wire of the sensor electrical connection.

A proper/good splice will not increase the resistance in the wire/path.

This reinforces what 383man said.
From the FCM for a 2001 DN.
An O2 sensor is a galvanic battery that provides the PCM with a voltage signal (0-1 volt) inversely proportional to the amount of oxygen in the exhaust. In other words, if the oxygen content is low, the voltage output is high; if the oxygen content is high the output voltage is low. The PCM uses this information to adjust injector pulse-width to achieve the 14.7–to–1 air/fuel ratio necessary for proper engine operation and to control emissions.

The O2 sensor must have a source of oxygen from outside of the exhaust stream for comparison. Current O2 sensors receive their fresh oxygen (outside air) supply through the wire harness. This is why it is important to never solder an O2 sensor connector, or pack the connector with grease.

Four wires (circuits) are used on each O2 sensor: a 12–volt feed circuit for the sensor heating element; a ground circuit for the heater element; a low-noise sensor return circuit to the PCM, and an input circuit from the sensor back to the PCM to detect sensor operation.

Oxygen Sensor Heater Relay: If the vehicle is equipped with 4 oxygen sensors, a separate oxygen sensor relay is used to supply voltage to the sensor heating elements. This particular relay is used only for the 1/2 and 2/2 downstream sensors. Voltage for the other 2 sensor heating elements is supplied directly from the ASD relay. Refer to 8, Wiring Diagrams to determine which relay is used.

To avoid the large simultaneous current surge needed to operate all 4 sensors, power is delayed to the 2 downstream heater elements by the PCM for approximately 2 seconds.

Oxygen Sensor Heater Elements:

The O2 sensor uses a Positive Thermal Co-efficient (PTC) heater element. As temperature increases, resistance increases. At ambient temperatures around 70°F, the resistance of the heating element is approximately 4.5 ohms on 2.5/3.9/5.2 and 5.9L engines. It is approximately 13.5 ohms on the 4.7L engine. As the sensor's temperature increases, resistance in the heater element increases. This allows the heater to maintain the optimum operating temperature of approximately 930°-1100°F (500°-600° C). Although the sensors operate the same, there are physical differences, due to the environment that they operate in, that keep them from being interchangeable.

Maintaining correct sensor temperature at all times allows the system to enter into closed loop operation sooner. Also, it allows the system to remain in closed loop operation during periods of extended idle.

In Closed Loop operation, the PCM monitors certain O2 sensor input(s) along with other inputs, and adjusts the injector pulse width accordingly. During Open Loop operation, the PCM ignores the O2 sensor input. The PCM adjusts injector pulse width based on preprogrammed (fixed) values and inputs from other sensors.

Upstream Sensor - Engine Equipped With 2 Sensors: The upstream sensor (1/1) provides an input voltage to the PCM. The input tells the PCM the oxygen content of the exhaust gas. The PCM uses this information to fine tune fuel delivery to maintain the correct oxygen content at the downstream oxygen sensor. The PCM will change the air/fuel ratio until the upstream sensor inputs a voltage that the PCM has determined will make the downstream sensor output (oxygen content) correct.

The upstream oxygen sensor also provides an input to determine catalytic convertor efficiency.

Downstream Sensor - Engine Equipped With 2 Sensors: The downstream oxygen sensor (1/2) is also used to determine the correct air-fuel ratio. As the oxygen content changes at the downstream sensor, the PCM calculates how much air-fuel ratio change is required. The PCM then looks at the upstream oxygen sensor voltage and changes fuel delivery until the upstream sensor voltage changes enough to correct the downstream sensor voltage (oxygen content).

The downstream oxygen sensor also provides an input to determine catalytic convertor efficiency.

Upstream Sensors - Engine Equipped With 4 Sensors: Two upstream sensors are used (1/1 and 2/1). The 1/1 sensor is the first sensor to receive exhaust gases from the #1 cylinder. They provide an input voltage to the PCM. The input tells the PCM the oxygen content of the exhaust gas. The PCM uses this information to fine tune fuel delivery to maintain the correct oxygen content at the downstream oxygen sensors. The PCM will change the air/fuel ratio until the upstream sensors input a voltage that the PCM has determined will make the downstream sensors output (oxygen content) correct.

The upstream oxygen sensors also provide an input to determine mini-catalyst efficiency. Main catalytic convertor efficiency is not calculated with this package.

Downstream Sensors - Engine Equipped With 4 Sensors: Two downstream sensors are used (1/2 and 2/2). The downstream sensors are used to determine the correct air-fuel ratio. As the oxygen content changes at the downstream sensor, the PCM calculates how much air-fuel ratio change is required. The PCM then looks at the upstream oxygen sensor voltage, and changes fuel delivery until the upstream sensor voltage changes enough to correct the downstream sensor voltage (oxygen content).

The downstream oxygen sensors also provide an input to determine mini-catalyst efficiency. Main catalytic convertor efficiency is not calculated with this package.

Engines equipped with either a downstream sensor(s), or a post-catalytic sensor, will monitor catalytic convertor efficiency. If efficiency is below emission standards, the Malfunction Indicator Lamp (MIL) will be illuminated and a Diagnostic Trouble Code (DTC) will be set.

Todd you said a mouthful. I am sure you cut and pasted that one. Makes you realize how much info we have to learn as techs just to stay on top of one brand. Thanks for posting that info as I never thought about posting the info that way. Ron

Good info, some of which is new to me, personally.

But a lot of it may well not apply to the OPs '01 5.9.

And I would still weigh the costs vs the benefits before I spent the time and money to change the down stream(s) on this vehicle unless there was a direct indication of a problem with it.

So where does that leave us on the O2s that are universal and require the plug to be spliced on. The Bosch is original on a lot of vehicles and when you buy the replacement, it often needs the particular plug spliced on.

Yes you can solider them and then use a good quality heat shrink tube. Been doing it for years no problems. make sure you solider them.

another issue is, ? some mopars do not like bosh , not sure bout ngk.. the factory o2 are ntk and you can get them at napa,zone, or o reillys.. and of course the dealer..