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Mike A
Dodge Dakota
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3/21/2006
09:01:18
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 Subject: Speed sonsor location
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Message:
1990
4WD
3.9
Automatic w/OD
I am looking into why my OD will not engage. I had a friend scan the computer. There is a speed sensor code. While driving the sensor reads 0. O2 reads a pretty flat line with very little flucuation. Everything else looks good. Vehicle shift up well to 3rd gear.
History: I was driving and all of a sudden OD disengaed. It dropped to 3rd. Then OD would kick back in. It was as if there was too much load on the engine/trans and it would down shift. After awhile I was able to anticipate when OD would kick out. It was as if the engine was loading up like I was going up a hill. I let is sit for months before bringing it in to a trans shop. The trans was leaking and I never put ATF +4 in. I always used Dextron. They fixed the leak and drove it. The trans shifted fine. I picked it up and it drove fine all the way home. About 2 weeks later it began doing the same thing. It became much worse in a short period of time. Now there is no OD. The scan tool said the OD sol was not engaging. The speed sensor reads 0. The temp sensor reads 188.
My thoughts: I don't think it's an electrical short due to me being able to feather the gas to keep it in OD. I believe it to be a sensor of some sort. I'd like to replace the speed sensor to start, but don't know where it's located. I've seen pic of one on the trans extension housing and on the rear differential.
Question: Do either of these (speed sensors)effect OD operation? What are the necessary inputs the computer needs to engage the OD solonoid? I have a feeling this is a rather easy fix (gut feeling). Anyone else have this problem before?
Thank you for your input.
Mike
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Chris
Dodge Dakota
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3/21/2006
14:52:43
|  RE: Speed sonsor location
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Message:
I had the same problem on my 93/3.9/auto/2WD, where it wouldn't go into overdrive when it was really hot weather. Generally, after driving a while, it would start going into OD. It got worse where I had to drive it further and further before it would click into OD. I read back the fault codes and it indicated a faulty speed sensor. I replaced it and it fixed the problem. It's a little device that attaches to the trans at the speedo drive, and then the speedo cable attaches to the sensor. Disconnect the cable, unplug the wires, remove the sensor, put on the new sensor, connect the cable and wires. Done. Good luck.
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GB2000
GenIII
3/21/2006
17:26:57
| RE: Speed sonsor location
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Message:
If it's the one I'm thinking of...on the tailshaft of the tranny...when you remove it, watch your head, it'll dump tranny fluid all over you.
Josh Blackshire - Founder, OhioDakotas.NET
Red 98 Dakota Sport - Check it out!
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Mike A
Dodge Dakota
JOIN HERE
3/21/2006
18:21:34
| RE: Speed sonsor location
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Message:
Thanks Chris and GB2000 for your replies.
Chris, did your speedo work fine when you had problems with the OD? Mine is working fine.
I'm gonna go out right now to check it out. I'll let you know what I find. Stay posted.
GB2000, is the one you are referring to have the speedo cable attached to it too?
I looked at the cost of a speed sensor, is 120.00 about right?
Thanks again guys! Let you know the outcome real soon!
Mike
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Mike A
Dodge Dakota
JOIN HERE
3/21/2006
19:05:24
|  RE: Speed sonsor location
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Message:
ok... sensor came out in record time (8 min.) I must have been lucky. Anyway, when I removed it (like GB2000 said) fluid came out. But the fluid looks like chocolate milk. It's not black, just kinda choclate looking and thick. What is it. It doesn't smell burnt.
Also, I want to test the sensor. How does one go about doing that?
Thanks again guys!
Mike
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Scott C.
Dodge Dakota
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3/21/2006
19:42:38
| RE: Speed sonsor location
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Message:
testing that sensor.. well you have to put it back in... jack up the rear so the tires are off the ground and support it... that sensor i believe produces an AC Voltage signal... what ya have to do is get a volt meter set it to AC Volts... leave it unplugged and take the leads of the meter and touch the connectors you should see a voltage signal... or you can take and try to ohm it out... ohming it out can tell 3 different things.... it can tell ya if its open meaning the feild inside it is broken cause its a magnetic sensor, it has low resitance meaning its good or high resistance meaning its bad... testing it for a voltage signal is the best way....
Scott C.
Royal Auto
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GB2000
GenIII
3/21/2006
23:24:43
| RE: Speed sonsor location
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Message:
On my 98 it just had a harness clipped into it...not sure how different ours are from each other. And it only cost me I think $28 at Autozone.
The description of that fluid kinda makes me a lil nervous...my fluid is a nice cherry red. Brown and chocolate milk like doesn't sound good. Though at least it's not smelling burnt. How long since it's been changed? Might just be old and needing replaced?
Josh Blackshire - Founder, OhioDakotas.NET
Red 98 Dakota Sport - Check it out!
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Mike A
Dodge Dakota
JOIN HERE
3/23/2006
10:23:08
| RE: Speed sonsor location
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Message:
The sensor was put back in. The truck was jacked up and placed into gear. I'm getting nothing out of the speed sensor. I'm getting 4.88 volts to the sensor though. Is this right?
I removed the sensor and checked for resistance. At times it was open and other times it's closed with very low resistance. So, the speed sensor is bad. Will this cause the OD to not engage? If I spend 120.00 for the part and it still doesn't fix the problem I think its a waste of money. There isn't anything else wrong with the truck. Just no OD. Will the speed sensor cause a NO OD condition?
The chocolate milk fluid... It's getting replaced. I think it is water mixed with tranny fluid. I'll check the vent hose. How do you flush the tailshaft of the tranny? Is there a drain plug? Filler plug?
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