Oxygen sensor wiring: 3.3/3.8l '99 t&c

Last Edited By Krjb Donovan
Last Updated: Mar 11, 2014 07:48 PM GMT



I hope you can help :-) I am trying to connect the signal wire from the upstream and downstream Oxygen sensors to a EFFIE I cannot seem to find them and truly if at all possible would like to find a place to connect to in the engine bay that is easier to access then the PCM..was told by the dealer that they were on 30 and black/dark green color and 51 and tan/white color wires on the PCM.

In looking at my Childers book it says that I need to take out PDC AND the Battery to remove the cover to the PCM. The whole point of this in case your wondering is that I installed a HHO system and without being able to regulate the Sensors with the EFFIE they just dump more fuel in the engine when it senses that it is running lean due to the improved burn with Hydrogen. Any help to allow me access to those signal wires on the Oxygen sensors is very very welcome. The downstream one is a piece of cake but the upper stream one....well a whole different beast!

Thanks again for your help.

By the way I installed a HHO system before on my 1984 diesel F250 and improved my MPG from 1-17 all around to 21-2 all around. It was easy to install due to no Computer or sensors!

Looking forward to hearing your thoughts and comments



ANSWER: Hi Federico, Thanks for all the details but what is the year/make/model/engine(L) in your vehicle?

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QUESTION: Sorry about that it's a 1999 Chrysler Town and Country Limited front wheel drive with a 3.8 Liter engine :-)

Tried to give you lots of details to make it easy and forgot THE most important Lol.

Thanks for the fast response!

ANSWER: Hi Federico, According to the wiring diagram the black/dark green signal wire on pin 4 of the upstream oxygen sensor goes directly to pin 30 of the pcm with no intervening disconnects. It would appear that you will have to splice into the wire itself. The tan/white signal wire on pin 4 of the downstream sensor plug goes to a light gray color disconnect at the left front corner of the engine compartment on its pin 10 of the 10-pin coupling. It is located on a harness that run along the left-side frame rail and then turns the corner at the front of the compartment and is attached mechanically at the disconnect to a narrow bracket near the left edge of the radiator. The wire continues from there to pin 51 at the pcm. So you should be able to tap off there at the disconnect. That is how it stands according to the wiring diagrams from '98 that I have and which I have good reason to believe are applicable through the '00 model year. Roland PS Thanks for the rating and the nomination. You are entitled to do it again with each question that I answer, so if this has proven helpful feel free to give me a second nomination. Thanks again.

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QUESTION: Thanks for the answer, is there any place where I can access the black/dark green directly? I found a big connector in the engine bay on the right side of the engine on a bracket right with a red spade above the exhaust connector from the front one to the back manifold exhaust, which if it goes there it would be very easy. Also do you have a diagram of the ten pin as I never know which is the one or 3 or 10 in a connector...I'm more picture oriented specially to electric things!

Thanks for your help I think it will come together with your help!


Hi Federico, No, the black/dark green is shown as an unbroken/unspliced/undisconnect wire directly between the pcm and sensor so I see know reason for it to go to big connector that you describe. The other wires on the same plug at the sensor do go to either splices or a disconnect, but not the signal wire itself. As to the 10 pin disconnect, it is rectangular with 2 rows of 5 pins each. The 6-10 pins are in a row on the flat side of the disconnect. 6 and 10 are at the ends of the row of 5. You should find the pin numbers to be etched in the plastic and certainly the wire color will reveal itself. I also checked the '02 manual and find that it has eliminated the pathway through the 10-pin disconnect so both signal wires are not accessible except at either end or by puncturing through their insulation. Wire colors as well are different. But I believe everything I described earlier is accurate for your '99. Roland PS Thanks for any 'rating' activity you would wish to offer me.


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