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agrazela
Dodge Dakota
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7/16/2004
12:36:52
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 Subject: No O/D or CC; 1993 3.9L auto; Test VSS?
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I have a 1993 Dodge Dakota 3.9L v6 with 4 speed automatic transmission. Neither overdrive nor cruise control are functioning. I suspect the Vehicle Speed Sensor (VSS) is faulty.
Before dropping $80 for a new one at Autozone, is there any way to test the current sensor to see if it is functioning properly?
By the way, this VSS has a speedometer cable hookup...and the speedo seems to work fine. Also, this is a two-wire hookup, not three-wire like my Chilton's manual electrical diagram says (strange, eh?). Finally, when I unhook the electrical connector from the VSS, it does NOT throw a code.
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93Dak
Dodge Dakota
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7/16/2004
13:24:27
| RE: No O/D or CC; 1993 3.9L auto; Test VSS?
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Are your backup lights working?
I ran into this same situation, and let me explain what happened.
When I first bought my 1993 Dakota, 4x4, 3.9, auto, it wouldn't always start. The neutral safety switch was not grounding the circuit as it should when the vehicle is in park or neutral.
I checked my linkages and my engine mounts and couldn't find anything wrong. Just every once in a while it wouldn't line up and make contact. So I spliced into the wiring and grounded that circuit. The truck started up great and ran, but neither overdrive nor cruise control would work.
I wired in a push button switch so that I can hold the button to ground the circuit. (When I release, it doesn't ground it anymore.) This way, if the linkage doesn't line up, I can start my truck by holding the button and turning the key.
Is it possible that someone has done some wiring like I did? I think that a neutral safety switch that is ground all the time would cause this too.
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93Dak
Dodge Dakota
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7/16/2004
13:29:01
| RE: No O/D or CC; 1993 3.9L auto; Test VSS?
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By the way, the speed sensor could cause this problem too, although I don't know anything about the speed sensor on these trucks... (On my older K-cars, there were two wires on it, and if you put an OHM meter across the leads as you turn the gear on the speed sensor you would see 8 pulses of a certain resistance with breaks of infinite resistance in between for one full turn.)
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agrazela
Dodge Dakota
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7/16/2004
14:29:08
| RE: No O/D or CC; 1993 3.9L auto; Test VSS?
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93Dak,
Thanks for the replies. I must have seen one of your previous posts, because I have checked my backup lights (they do come on in reverse). I have also "jiggled" the shift stick while driving to see if maybe there was a slight out-of-position thing going on with the shift position sensor...no dice.
I have noticed that the truck will not start when the shift sensor plug is unhooked; however, if you start the truck and THEN unhook the sensor, it continues to run (i.e., does not shut off). I will try starting, unhooking the shift sensor, then running to see if O/D and/or CC operate.
As for the VSS...you may have inadvertently answered my question. I ran an ohmmeter across the two leads. I got 8 clicks on one rotation, alternating between infinite resistance and NO (that is, zero ohms) resistance...is it supposed to alternate between infinite resistance and "some" resistance (i.e., greater than zero but less than infinite ohms)?
Also, why is it that I get no code even when I purposely unhook the VSS? Is this because the computer cannot send a reference voltage to a 2-wire sensor? (I have purposely unhooked other 3-wire sensors, for example the throttle position sensor and the MAP sensor, and gotten the expected codes).
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93Dak
Dodge Dakota
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7/16/2004
16:01:38
| RE: No O/D or CC; 1993 3.9L auto; Test VSS?
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Not sure why you wouldn't get a code when you disconnect it. I believe that if you disconnect the O2 sensor, you'll get a code (and that is two wire).
I thought that the resistance in the speed sensor was actually a value, but it was high, like 100k. I just can't remember now.
But you could be on to something. If there is either no resistance or infinite resistance, then there wouldn't be a continuous voltage. Instead of pulsing low-high, it would pulse zero-high.
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93Dak
Dodge Dakota
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7/16/2004
16:13:15
| RE: No O/D or CC; 1993 3.9L auto; Test VSS?
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I may have made a mistake. (It's been a long time since I've played with one of those sensors.)
It may be 0 resistance and a value and the value is high (like 100k). I don't think that it ever goes to infinite resistance.
You might want to check to see if the middle wire on the neutral safety switch is grounded. It is a difficult check because the vehicle cannot be in park or neutral. Whatever color the middle wire is (either brown or blue-yellow sticks in my head), it comes up in the bundle if wires that are attached to the firewall under the hood. That's where I tapped into mine to run my switch.
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93Dak
Dodge Dakota
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7/19/2004
09:01:18
| RE: No O/D or CC; 1993 3.9L auto; Test VSS?
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Here is a quick test to see if you have a problem with the neutral safety switch or circuit. Start the truck, then unplug the neutral safety switch connector. If you cruise and overdrive work, then you have a problem with the neutral safety switch.
It is located on the driver's side of the transmission below the driver's door. It is a big rubber connector with three wires.
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agrazela
Dodge Dakota
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7/19/2004
11:33:25
| RE: No O/D or CC; 1993 3.9L auto; Test VSS?
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93Dak,
I will try the neutral safety shift plug idea. I would have tried it over the weekend, but with four kids, two dogs, wife working weekends and both a boat and a camper renovation in process, even simple stuff on the truck falls way down the list!
Maybe I will try it at lunchtime at work today...my job is the only time off I get!
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agrazela
Dodge Dakota
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7/20/2004
01:54:41
| RE: No O/D or CC; 1993 3.9L auto; Test VSS?
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93Dak,
I checked the neutral safety plug at lunch as proposed...no change in operation.
I will try other things and keep posting my results.
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agrazela
Dodge Dakota
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7/20/2004
01:59:41
| RE: No O/D or CC; 1993 3.9L auto; Test VSS?
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93Dak,
I checked the neutral safety plug at lunch as proposed...no change in operation.
I will try other things and keep posting my results.
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93Dak
Dodge Dakota
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7/20/2004
09:20:43
| RE: No O/D or CC; 1993 3.9L auto; Test VSS?
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Well, that's too bad. I was really hoping that the coincidence between cruise and overdrive had to do with that circuit.
Is there any chance that someone grounded that circuit permanently by splicing into the wiring somewhere? I'm all out of other ideas. (Someone would do this if the neutral safety switch wouldn't make contact in park and neutral, so the vehicle wouldn't start.)
I guess I have one more idea. The neutral safety circuit provides a ground to the starter relay. I wonder if the relay could be broken and providing a ground all the time. The starter relay has six pins and it is located in the black box above the driver's side front tire.
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Nathanr87
Dodge Dakota
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10/06/2010
14:44:58
|  RE: No O/D or CC; 1993 3.9L auto; Test VSS?
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Why would you pay 80$ for a VSS
Http://www.carpartswholesale.com/
has them for about 25$ with shipping autozone and checkers way over price for that unit.
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