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Thread: Ford canít reprogram my Speedometer. Need solid advice.

  1. #1
    is fixin shit that's not broke hav24wheel's Avatar
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    Default Ford canít reprogram my Speedometer. Need solid advice.

    Built myself a ratted up pickup out of a 2007 Police Interceptor and a 66 F250. Changed the tire size and the gear ratio, the speedo is WAY off. Took it to Ford and they said they couldnít do anything with it because of the tires and gears I picked are not factory options. I was going to put a Dakota digital speedo interface into it to correct it. BUT, Iím not sure if I should tap into the trans output shaft speed sensor, or where. And if I do that, will it mess up the traction control, ABS, or the trans shifting. Any advice on this?

  2. #2

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    Three ways to go about it.
    This is my order of preference, but you're not me and all will work with varying degrees of success:
    1. Ideally, contact a company selling ECM tuners, such as SCT (I like Justin at VMP tuning in Florida) or one of the others--Bully Dog, Sniper, etc. This is pretty easy for them and gives you access to a bunch of other tuning options.
    2. The Dakota Digital setup (or similar pulse converter) can install between the speedometer and the speedo source. I'm not sure on a 2007 whether the ECM sends a signal to the gauge panel with the vehicle speed (are you using the Police Interceptor gauges?). If the ECM sends data to the instrument cluster, you may have to put the converter between the speed sensor and the ECM. That will throw off the ECM calculations a little, but so did putting the wrong size tires on. I'm not sure if the effects are meaningful (how much of a discrepancy is there? I would guess you put much larger tires on?)
    3. Use an aftermarket speedometer and get the speed directly from the output speed sensor. This still leaves the ECM looking at the wrong vehicle speed.

    Any approach that doesn't involve reprogramming the ECM is going to leave it reading off--again, I suspect you put on larger tires, so it will think the vehicle is traveling slower than it actually is. Also, it's riding in a vehicle with different handling characteristics (weight distribution especially) than the CVPI. I don't know how that will affect the ABS and Traction Control, but I think it might affect shift points for economy (engine speed and throttle/accelerator points are more important in transmission gear choice, so you should be okay there).
    I wouldn't worry too much about it, but talking to someone with tuning and engine swap experience (another plug for VMP, and SCT tuners) can probably get you a program that does a lot more than just fixing the speedometer error.
    If you're not driving this in extreme weather or on a track, any of these will be just fine, including option 2a, skip the Dakota Digital price and use a cheap eBay version.

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    Member EaOutlaw1969's Avatar
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    https://www.autometer.com/gps-speedometers possible easy option

    Hot Rod TV show did a very similar swap I do not remember what they did with the speedometer or harness but it is worth watching you may get some ideas for your conversion that you may not have thought of.

    https://www.hotrod.com/articles/hot-...100-crown-vic/
    Last edited by EaOutlaw1969; 12-28-2019 at 06:43 AM.
    2007 Ford Crown Victoria LX Sport

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    I'm an air-conditioned gypsy gadget73's Avatar
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    Seen this done on a Marauder. Not sure what the specific tuner used was, but basically you just set the rear gear ratio and tire size and it fixed the speedo. NBD.

    The trans shift scheduling relies on proper speedo input too, so you really want to fix it in the computer.

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    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

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    A tune would be the simplest fix and SCT is the ideal one to use because more people have experience with them. Not sure if Blue Oval Chips is still in business but that's who the CVN guys swear by for tuning these cars. I'm sure pretty much anybody that tunes and sells tuners would be ok though. I understand Bama performance is also great to deal with.

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    Hobbit
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    is fixin shit that's not broke hav24wheel's Avatar
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    I swapped in 4.56 gears, and have a 245/65R17 tire on it. Iím using the Dakota product on a different vehicle, and it worked great on that but I donít have ABS or any of that. Iím just wondering if I where to tap into the signal on this vehicle to change the speedo reading, without messing up the abs/traction control/trans shifting. Iím using the police guages. Basically just did a sheet metal swap. Itís got the car dash and all that in it still. I know that thereís a speed signal wire at the ECM, and Iím guessing the ECM sends the signal to the cluster, because thatís the color of the wire that everything says is the vehicle speed wire. The wires at the sensor on the trans are totally different colors. So, basically getting the signal changed right at the cluster would work the best?

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    is fixin shit that's not broke hav24wheel's Avatar
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    Or is that going to still make the computer hit the speed limiter early because the computer will still think it’s going faster than it is? It’s about 20 mph off at 80. So it reads 80 and I’m actually going about 60.

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    +1 a proper tune from a non-ford source (Marty, SCT, HP-tuners, etc) will fix that. I'd say go the do-it-yourself route with an SCT unit if you just want to change gear/tire settings and not much else over the canned tune. Quick an easy. If you need to delete EVAP/EGR/rear O2s, you'll have to get something specialized from HP tuners as they are the only ones left that can actually tweak emissions related stuff for 07+. At least until the federal lawsuits finish. Feds killed SCT in that regard about a 6 years ago.

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    Did some math to find the ratio of the new tire size to stock tire size and the gear setting to use in the PCM is 4.10 if you don't tweak the tire size setting.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
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    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

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    is fixin shit that's not broke hav24wheel's Avatar
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    Well, I could use a rear O2, EGR, EVAP delete as well, main concern was the speedo at the moment. But a custom tune might be down the road because I have full length headers and free flowing 3 inch exhaust too, and plans for Cams later down the road. BUT 4.10s isn’t a option in the computer, but that’s talking factory stuff that I have access to at this moment. I was basically hoping to wire in the interface/converter I already have on hand to make the speedo right so I can just drive. Lol.
    Last edited by hav24wheel; 12-28-2019 at 01:59 PM.

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    is fixin shit that's not broke hav24wheel's Avatar
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    Here’s the two wires in question. The Green/yellow comes from the trans output shaft speed sensor, and the Gray/black is the one going into the cab that should be the vehicle speed signal wire. Just not sure the consequences of changing the signal to the computer vs from the computer.


    Sorry about the multiple posts, I’m kinda all over the place on things right now. Lol
    Last edited by hav24wheel; 12-28-2019 at 02:22 PM.

  13. #13
    I'm an air-conditioned gypsy gadget73's Avatar
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    I would definitely not do that. You'll probably get some strange error code if the engine rpm and selected gear don't jive with what the PCM sees on the trans output shaft speed sensor.

    86 Lincoln Town Car (Galactica).
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    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

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    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  14. #14
    is fixin shit that's not broke hav24wheel's Avatar
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    Ya, I’m not sure! I was hoping to find out here, because on my 99 E350 van I did a 4x4 conversation on, I had to change the signal coming from the trans to the computer, because the type of sensor between the 4x4 pickups and the Vans have a different location for the speed sensor. The pickups where in the rear axle and the vans in the tailhousing of the trans and the 4x4 trans didn’t have that, so used the output shaft signal to make the speedo work, and that works without codes/shifting issues. So, that’s why I thought it would work on this too BUT the van doesn’t have traction control or functional ABS.

  15. #15
    I'm an air-conditioned gypsy gadget73's Avatar
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    Its also older, which might matter.

    I remember Seneeb did a gear swap in a 97 and changed the gear on the VSS to correct the speedo. He said it had shifting problems and the speed limiter kicked in at like 70 because it was rpm based. The speedo read correctly but the ECM wasn't using that signal to control things. He tuned it for the different gearing and it quit being stupid.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  16. #16
    Beater gonna beat sly's Avatar
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    Yeah... output shaft sensor and vehicle speed sensor have to jive for the PCM to be happy. An SCT tuner should allow you to change the gear ratio to 4.10. That would sort the speedo. If you're using the 2007 cluster that is. I think 06+ (maybe earlier) use a signal from the PCM to control the speedometer instead of the VSS signal to the speedo. Tapping the VSS signal for an aftermarket speedo would be a much easier solution.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
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    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

  17. #17
    is fixin shit that's not broke hav24wheel's Avatar
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    So thereís a output shaft sensor and a vehicle speed sensor? Whereís the vehicle speed sensor than? Thereís nothing behind the output shaft sensor in the case of the trans, the tail housing is bare, has provisions but nothing installed and nothing on the rear diff, but thereís the wheel speed sensors. .
    I see where your saying a tuner/tune would be the easiest way. I was hoping for a cheaper way I guess. I mean I only have $1000 into this whole project so far, and was tryin to keep it as cheap as possible. So ya, I guess more research is in my future.

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    Last edited by hav24wheel; 12-28-2019 at 09:27 PM.

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    04+ only have OSS which sends signal to both PCM and speedo. Older cars used a second mechanical sensor for the speedo.

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    Beater gonna beat sly's Avatar
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    Quote Originally Posted by Mr Bean View Post
    04+ only have OSS which sends signal to both PCM and speedo. Older cars used a second mechanical sensor for the speedo.
    Ah... that's the year that things changed then. Bummer they dumped the VSS. Looks like a tune would be the best option.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

  20. #20
    is fixin shit that's not broke hav24wheel's Avatar
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    Welllllll, I’m waiting for a message back from Dakota Digital to see if they have any idea about if changing the signal from the oss will affect anything. I honestly can’t see spending the $ on the tuner at this time if I absolutely don’t need to. But after I drop the$ on cams than I’ll definitely get a tuner to change everything I need to.

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