QuestionQUESTION: Okay, I'm hoping you might be able to give me some advice on a 94 Caravan 3.0L 3 Speed automatic. My Speedometer would cut in and out periodically during humid days. Now the Speedometer has completely stopped working. My computer gave me a Code 15 No signal from the speed sensor, So I replaced the Speed Sensor , And it still don't work. I used a multi-meter too check the plug connections, and it tests fine too the next plug in the wiring harness... What May i be missing ?
ANSWER: Hi Russell,
You didn't mention which engine is involved but basically you need to make sure that the three wires from the sensor to the powertrain control module are patent. The orange goes to pin 7, the black/light blue goes to pin 4, and white/orange goes to pin 47 and that the first and third are not shorted to ground (the second is a common sensor ground wire). There should be 9V on the orange when the ignition is in the run position.
Roland
---------- FOLLOW-UP ----------
QUESTION: Okay, I just Did a little Check with my Volt Meeter...
On the Sensor there is a plug with 3 Wires, A white one, a purple one, and a Black one with red(Orange) Stripe. From my Battery, the white wire has no voltage, The Purple Wire is giving me 13.95v and the Black with a stripe is giving me 8.05v
ANSWER: Hi Russell,
Are you looking at the colors of the sensor-side of the wires or the harness wires? My manuals for '93 and for '95 (I don't have the '94) are identical as to wire colors. I presume that you mean by "from my battery" that one of the voltmeter leads is connected to the - post clamp. I can't explain why you have the wire colors that you do have. But in any case I would suggest that you check the patency thru to the pcm pins that I listed. That way we can sort out which is which. If that checks out, then about the only other possibility is that the gear on the end of the speed sensor is damaged/or not mating with the gear on the output shaft gear of the transmission. You could check that out by lifting the right front wheel off the ground and turning the wheel by hand with the ignition in the run position and observing whether you are getting voltage pulses on one of those three wires, typically about 8 pulses per revolution of the wheel. I can't explain why you are getting 14v on black/red(orange) and I would believe that should be showing 8V or less if it is the signal wire. For history, the way that speed sensors on the 3-speed automatic become damaged is if someone pulls the right side half shaft out of the transaxle without first removing the speed sensor. That will strip the gear on the end of the sensor.
Roland
---------- FOLLOW-UP ----------
QUESTION: Okay, the wires i was looking at are on the Sensor. The wires that come off the sensor its self, One of them does have 8v the other no volts, and the other has 14v and that is going from my Battery Post, too the volt Meter. As for the sensor, there is no gear on the sensor, it looks like a nipple if anything, or the back end of a standard 110v Light bulb. And if the gear end were too be damaged, would the computer still give me a code 15 ? And could the 14v on the black/red wire mean I have a short some were ?
AnswerHi Russell,
I have to beg ignorance of why there is battery voltage one of the wires, for if it were the "signal wire" I would think it would be shown 0 volts. But, in any case, I suggest that you remove the 60-way plug at the powertrain controller and see which wire is connected to 4, 7, and 47. As for the sensor tip, the one I am familiar with is from a few year earlier wherein it has a 2-wire setup instead of 3, so I suspect that the tip was redesigned, possibly to circumvent the damage events that I described. In any case sort out the wiring, and which ever one is connected to 47 should show voltage pulsing as you turn the right hand road wheel.
Roland
