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Speed Signal From Computer Wrong

Discussion in 'Stock 2006 -2010 Explorers' started by FStephenMasek, September 7, 2012.


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    1. FStephenMasek

      FStephenMasek Member

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      For a few months I've noticed that my Pioneer navigation unit was showing radically too-long trip times. Today I looked at a screen which shows that it thinks the vehicle speed is about one third the actual speed. It was running funny on a trip to LA earlier today, seeming as if the transmission was slipping. For a while, the AC was not blowing cold. I think all of this points to a computer problem. Has anyone else here had such problems? If so, what was the solution?

      I collect and restore old radios, mainly from the 1930s, for fun, and know electrolytic capacitors are not durable over the long run. Some newer flat screen TVs have been having electrolytic capacitor failures. I fixed one for a guy I was working with on a large abatement and demoliton project. Some guys on the old radio forum have also mentioned opening Ford computers and replacing bad electrolytic capacitors. However, before I try to take it apart, I thought to ask here, as it could be some other problem which is known to people here.
       
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    3. waskly

      waskly Well-Known Member

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      whats the radio set for input for the speed? the speed signal is off the abs module not the pcm.
       
    4. FStephenMasek

      FStephenMasek Member

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      I installed it in 2006, and it has been conencted to the speed (VSS) signal line at the PCM since then. From late 2006 to early 2012 it was working properly. All connections are soldered, and I checked the one at the PCM and found no problems. I pulled the Pioneer unit out today to look for wiring problems and found none there.

      I should also note that the rough downshift to first gear when stopping has also returned, although it does not happen all of the time. Just before the warrantly expired on mileage, it was at Santa Margarita ford for a few days, while their transmission guy worked on it. I spoke with him, and he told me that he had tried one fix, was not satisfied, so took it apart and did other things.

      There are now 129,000 miles on it.
       
    5. FStephenMasek

      FStephenMasek Member

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      I installed it in 2006, and it has been connected to the speed (VSS) signal line at the PCM since then. From late 2006 to early 2012 it was working properly. All connections are soldered, and I checked the one at the PCM and found no problems. I pulled the Pioneer unit out today to look for wiring problems and found none there.

      I should also note that the rough downshift to first gear when stopping has also returned, although it does not happen all of the time. Just before the warrantly expired on mileage, it was at Santa Margarita ford for a few days, while their transmission guy worked on it. I spoke with him, and he told me that he had tried one fix, was not satisfied, so took it apart and did other things.

      There are now 129,000 miles on it.
       
    6. waskly

      waskly Well-Known Member

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      vss from the pcm comes over the hs or ms can network. cant think of it off the top of my head.

      what trans sensor are you using for the speed control?
       
    7. FStephenMasek

      FStephenMasek Member

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      I have the Ford factory shop manuals. VSS is on Pin 1 of the PCM connector (see Page 24-9 of the 2006 Explorer, Mountaineer Wiring Diagrams manual). It goes to the front wipers and washers. The Pioneer AVIC-Z1 was their top of the line unit in 2006. It does not have facilities to conenct to any of the busses for obtaining speed information, simply one wire to connect to obtain the VSS signal. Again, this has been working well from late 2006 to early 2012.
       
    8. steve6534

      steve6534 Active Member

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      Have you looked at the diag screen on the Z1 to see if any pulses are detected ? Normally the unit uses GPS for speed and only relies on the VSS pulse for dead reckoning if GPS signal is lost (city with many tall buildings, tunnel, etc).
       
    9. waskly

      waskly Well-Known Member

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      Im very aware of pin1 on c175b, vsout. to wiper motor.

      on the radio what is the speed control signal configured to?

      since not every mfg has the same speed rating per mph. it should be 2.2hz per mph.
       
    10. FStephenMasek

      FStephenMasek Member

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      I don't know what the Pioneer unit does with the signal, but do know that the screen which shows vehicle speed and other hardware information shows a number which is about one-third (or less) of the correct value. I doubt I've previously looked at that screen. Perhaps it has been wrong all along. I see noo way to set the value.

      The wrong speed may explain why it has started showing very long trip durations, but it could be some other problem. It clearly has a good connection to the GPS antenna, and shows that.

      My main concern is not the navigation unit trip duration, but the rest of the Explorer. perhaps teh navigation unit trip duration being wrong the the odd behavior today are not even related.

      I know some Ford pickups have had computers which needed new capacitors.

      Has anyone here opened one of the units which is on the 2006 Explorer V8?
       
      Last edited: September 7, 2012
    11. waskly

      waskly Well-Known Member

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      i'll explain it easier, the pcm does not send a signal that goes 50mph 40mph 30mph etc, it sends out a hz signal, your audio deck, most likely since they did a transmission and had the battery off for an extended period of time, lost a setting. reconfigure the speed input to the unit.

      it should be set to 2.2hz for each 1 mph.
       
    12. briwayjones

      briwayjones Manual Master

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      I'm going to semi-hijack this thread. I've had a minor speed issue on my 2003 Sport since I got it. I'm the second owner, had 34,000 on it when I got it. It has stock size tires on it. The speedometer has always registered fast. The faster you go the more it's off. At 65mph it's off about 3-4mph.
       
    13. FStephenMasek

      FStephenMasek Member

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      Thanks, I understand, I have yet to find a screen where the frequency vs speed relationship could be set on the Pioneer.
       
    14. steve6534

      steve6534 Active Member

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      There isn't one. You can reset the calibration and let it learn again though. It takes hundreds of miles before it decides it has a good reference(in conjunction with the gyroscope to determine if the speed is on a level surface or not).
       
    15. waskly

      waskly Well-Known Member

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      are you comparing the speed dial to a gps unit?
       
    16. briwayjones

      briwayjones Manual Master

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      I'm comparing it to a scanguage. And the scanguage agrees with a permanent speed sign that I used to pass going to work. Using the scanguage on my other Explorer the scanguage and speedometer matched. The speedometer on that Explorer also matched the speed sign.
       
    17. waskly

      waskly Well-Known Member

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      speedometers unless its says "certified calibrated" are not dead accurate, they can be off 1-2 mph, if i had to guess the speedo on your vehicle the little motor that moves the needle is off. or someone poped the needle off and reattached it.

      also you said stock tires, does the tires match the sticker on the door? size etc?
       
    18. briwayjones

      briwayjones Manual Master

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      I've changed the tires. They are a different aspect ratio but same roll rate and diameter. Plus it did it with the OE tires on it anyway. Nothing changed.
       
    19. FStephenMasek

      FStephenMasek Member

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      I did some more research. I have a bench frequency counter which runs on 120VAC, not very useful in a moving vehicle. Then I realized that I have a battery-powered multi-meter with a frequency function. I connected that to the Pin 1 line, and the signal from the computer is 2.2 Hz per MPH. So at least that part of the car computer is OK. I'll try a hardware reset on the navigation unit, and if that does not help, loading the newest version of the software.

      Of course, this leaves me wondering why it felt as if the transmission was slipping, and the air conditioner was not working properly on Friday morning. Friday afternoon, Saturday,a nd today (Sunday), it ran fine, and the AC was cold. I did notice that the navigation unit shows the voltage while underway as 14.1 to 14.2. That seems on the high side.
       
    20. waskly

      waskly Well-Known Member

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      your voltage is fine.

      try to google the radio model owners guild.
       

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