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92 Dakota code 15 and noise

Discussion in 'Repairs, Maintenance, Help' started by Bob Lincoln, May 15, 2020.

  1. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    1992 Dakota, 241K miles, have owned it 16 years. This winter, I had the instrument panel out for maintenance, and after I installed it, I noticed that after awhile of driving (sometimes 15 miles, sometimes 30, but not right away, never when cold), I'd hear a clicking, almost scraping noise from near the left rear wheel. The speedometer needle also bounces slightly, but NOT wildly, which it didn't do before. I figured I disturbed it and didn't get it installed optimally when I connected it again to the instrument panel, and that it might need lubing. The speedo and odometer work normally.

    Well, after awhile when it got to sounding loud enough to get people's attention at low speeds, scraping, I checked further and found CV grease leaking out a bad split in the LF axle. I had it replaced, but the noise remained. Sometimes I can drive 30-50 miles with no noise, sometimes after 5 miles.

    Today I checked codes, as I need to get rid of a code 12 from disconnecting the battery, before inspection. I found that I have a new code 15.
    Now I'm wondering if the entire time, the pinion gear to the speed sensor on the transmission, where the speedometer cable connects, may be damaged, and that's the scraping. Or I pulled the cable up enough to only partially engage it. Thoughts? I don't want to buy unnecessary parts. Thinking I should first try to reinsert cable.
     
  2. ImperialCrown

    ImperialCrown Moderator
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    Speedometer cables can be lubricated. We used to have to do this whenever they got noisy or the needle wiggled.
    Any general grease (not wheel bearing grease) should be good.
    Pack a blob of grease at the end of the sheath, then slide the cable core back in, rolling it slightly to spread the grease as it enters. If the cable is very dry, you may have to repeat the process.
    [​IMG]
     
    valiant67 likes this.
  3. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    Thanks, but how would the cable have caused a code 15 with working speedometer and odometer, and a scraping noise that varies with the speed of the vehicle?
    Or maybe there is another issue such as a wheel bearing?
     
  4. AllanC

    AllanC Well-Known Member

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    The distance center is an attachment on the driver side of the tailshaft on the transmission. It has a mechanical shaft that turns and mates with the speedometer drive gear on the transmission output shaft. It also has a threaded connection that mates the square end flexible speedometer drive cable to the speed sensor. So the mechanical part of the distance speed sensor can function and drive the mechanical speedometer and odometer but have an internal electrical problem that causes code 15.

    Internally there is a wheel that has several magnets. As the transmission output shaft turns and turns the distance speed sensor shaft, the magnets pass by a reed switch and cause the switch to close. So the turning of the distance speed sensor shaft causes a pulsing signal to be sent through the 2 wire harness at the speed sensor to the PCM (powertrain control module). See attached image.

    Distance Speed Sensor.gif

    The sensors have a metal housing crimped around a plastic body. Dirt and moisture can infiltrate the sensor and cause problems with the dielectric grease on the inside. Uncrimp the metal surround and remove the rotating wheel and reed switch. You may be able to clean and get it to function again. Also check the male and female mating connectors for corrosion, debris, bent pins / receptacles. Also check the 2 wire cable from the distance speed sensor to the PCM.
     

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