Digital and Analog speedometer don't agree

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Craw

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Anyone else have this issue? Always has been this way since I bought from dealer. Even verified tire size with a tuner. Unsure which one to believe lol.

2013 Ram Sport
Tire 275-55-20
 

huntergreen

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A GPS could verify which is correct.
 

crash68

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The same speed sensor feeds both the digital and "analog style" speedometer.
If the needle is off drastically, there is probably a problem with the dash cluster. How far is it off?
 
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Craw

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2-3 mph at higher speeds. I am wondering if maybe my digital uses gps (built in) and the analog uses the actual gear.
 
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Tach_tech

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2-3 mph at higher speeds. I am wondering if maybe my digital uses gps (built in) and the analog uses the actual gear.
No it doesn't use GPS for any speed display. Could be something wrong with the actuator for the speedo or maybe parallax error.
 
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Craw

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No it doesn't use GPS for any speed display. Could be something wrong with the actuator for the speedo or maybe parallax error.

Would this be a warranty thing? I did a GPS test with phone and actual GPS and they both say Analog wins. The Digital read 69 then the analog, 2 GPS said 65. Tires at 41 PSI for the Falken Wildpeak AT3w rated of max 50 PSI So I know it ins't a tire pressure issue.
 

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No it doesn't use GPS for any speed display. Could be something wrong with the actuator for the speedo or maybe parallax error.
Careful, that’s not entirely true. The speed display in the Harmon GPS does not use any sensors to calculate the speed. If you bring up the trip odometer and look at present speed, that is GLS calculated. This was verified on my Cherokee when I changed tire size. Before the change, the radio and the gauge cluster matched. Afterwards, they did not.
 
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Craw

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Careful, that’s not entirely true. The speed display in the Harmon GPS does not use any sensors to calculate the speed. If you bring up the trip odometer and look at present speed, that is GLS calculated. This was verified on my Cherokee when I changed tire size. Before the change, the radio and the gauge cluster matched. Afterwards, they did not.

So maybe my gps sucks? lol
 

Tach_tech

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Careful, that’s not entirely true. The speed display in the Harmon GPS does not use any sensors to calculate the speed. If you bring up the trip odometer and look at present speed, that is GLS calculated. This was verified on my Cherokee when I changed tire size. Before the change, the radio and the gauge cluster matched. Afterwards, they did not.


I'm only referring to the analog read out and the digital read out in the cluster, not the factory navigation.

Both the digital and analog speedometer are controlled via bussed messages from the PCM that receives the vehicle speed message from the ABS module, so it is true.

The factory NAV does use GPS signal for the speed read out in the nav display.
 

Tach_tech

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Would this be a warranty thing? I did a GPS test with phone and actual GPS and they both say Analog wins. The Digital read 69 then the analog, 2 GPS said 65. Tires at 41 PSI for the Falken Wildpeak AT3w rated of max 50 PSI So I know it ins't a tire pressure issue.

I cant find any TSB's or anything that relate to your issue.

It could be a faulty cluster, best way to tell would be with a scan tool and monitor vehicle speed message in the PCM or ABS module and monitor it in the cluster as well. If the cluster data on the scan tool shows a different number than what the digital read out shows then chances are something is wrong with the cluster.
 
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Craw

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I cant find any TSB's or anything that relate to your issue.

It could be a faulty cluster, best way to tell would be with a scan tool and monitor vehicle speed message in the PCM or ABS module and monitor it in the cluster as well. If the cluster data on the scan tool shows a different number than what the digital read out shows then chances are something is wrong with the cluster.


sigh, guess I wont use the digital one. Go old school, I already know the digital is off due to the 2 seperate gps and analog agree. I do have a scanner always hooked up and that agreees with the digital (so reads the pc).
 

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So the digital read out in the cluster agrees with what your scanner shows? Could just be the way it is, best way to verity would be with a scan tool that can read all the modules as I said before. If it doesn't bother you that much I wouldn't really worry about it.

Speedometers don't have to be 100% accurate, by law they have to be within something like 3mph of actual speed, police vehicles speedometers have to be within 1-2mph i believe. I may be slightly off on those numbers though.
 

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I'm only referring to the analog read out and the digital read out in the cluster, not the factory navigation.

Both the digital and analog speedometer are controlled via bussed messages from the PCM that receives the vehicle speed message from the ABS module, so it is true.

The factory NAV does use GPS signal for the speed read out in the nav display.
that's why i corrected you, because you said it doesn't use the GPS for any speed display, which is not entirely true. The factory radio uses GPS to calculate speed, and will display that speed if you look at the trip odometer. the new 4C radios, however, use the truck's speed sensor and not GPS.
 
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Craw

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Thank you for the responses :). I will see maybe if I can get the dealer to take a peek once I bring it in for installation of my tow hooks and maybe the brake controller. Still deciding between OEM with convenience or P3 for functionality.
 

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