Speedometer off (tried two different calibrators)

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Hangumhi

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May 19, 2021
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Washington state
My speedometer is off by 6-9mph. Higher speeds (above 50), its off by about 6mph. Lower speeds (between 20 and 50) it's off by approximately 9mph.

It has a four inch lift and 35" tires. It is an 08, JKU Rubicon.

So, I bought two different calibration devices. One is the ECRI and the other is the Vgate iCar Pro. The ECRI uses their own proprietary app. I use the Jscan app with the Vgate. Both units connect fine and say that the programming is successful when I change the tire size...however absolutely nothing changes with the speedometer. I have worked with both Jscan and ECRI, and both companies are stumped. I have done absolutely everything they can think of but the speedometer stays the exact same. I have even reprogrammed for 40" tires...no difference in the speedometer.

Any thoughts on where I can take this for a next step attempt?
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I wonder if the two apps are over riding each other.

Is this a manual or auto? Not as important for a manual as it is for an auto, though it is always good to know how fast you are going.

Pretty much everyone here uses JScan, at least that is the one that gets brought up the most. I would ensure that the other is not running in the background before doing anything.

Wait... I'm pretty sure that Jscan pulls the speed from the computer for that screen, meaning that something is wrong with your speedometer and if that is the case and your speedometer is saying something else... hmm.. bad speedometer? We need to figure out what reading is incorrect. What does a gps app say?
 
Thank you very much for the response. It is an automatic. I deleted the ECRI app before installing JScan. The GPS reads pretty much the same as the JScan trail mode that shows me the mph as I drive. I'm also wondering about a broken speedometer. I wonder how I could determine if the speedometer itself is broken? Is that something that can be adjusted or easily repaired/replaced?
 
Hangumhi said:
Thank you very much for the response. It is an automatic. I deleted the ECRI app before installing JScan. The GPS reads pretty much the same as the JScan trail mode that shows me the mph as I drive. I'm also wondering about a broken speedometer. I wonder how I could determine if the speedometer itself is broken? Is that something that can be adjusted or easily repaired/replaced?
Click to expand...
Also, a representative from JScan worked with me for a good hour today and they were stumped as well. They too thought it might be a defective speedometer.
Tire speed sensors wouldn't have anything to do with it would they? I replaced the rear speed sensors today because I received a code within the JScan app that said I had faults in the rear tire speed sensors. The faults are gone now but still no difference in the speedometer situation. Thanks again for the help; I really appreciate it.
 
The speed sensors are probably just for the braking ABS.

I have a 08 and used my Hypertec prrogrammer and had no issues. All the changes happen in the ECM so if the speedometer still works then it's good. Might have to go to a Dealer and have them do it if they will.
 
I can't recall but I thought the speedo and tach needles moved in tandem to the same relative position during the test.

Here's the procedure...

ACTUATOR TEST
The instrument cluster actuator test will put the instrument cluster into its self-diagnostic mode. In this mode the instrument cluster can perform a self-diagnostic test that will confirm that the instrument cluster circuitry, the gauges and the indicators are capable of operating as designed. During the actuator test the instrument cluster circuitry will position each of the gauge needles at various calibration points, illuminate each of the segments in the Vacuum-Fluorescent Display (VFD) units, and turn all of the indicators ON and OFF again.

Successful completion of the actuator test will confirm that the instrument cluster is operational. However, there may still be a problem with the CAN or LIN data bus, the Powertrain Control Module (PCM), the Totally Integrated Power Module (TIPM), the Controller Antilock Brake (CAB), the All-Wheel Drive Control Module (AWDCM), the Occupant Restraint Controller (ORC), the compass module, the Sentry Key REmote Entry Module (SKREEM) (also known as the Wireless Control Module/WCM), or the inputs to one of these electronic control modules. Use a diagnostic scan tool to diagnose these components. Refer to the appropriate diagnostic information.


1. Begin the test with the ignition switch in the OFF position.
2. Depress the odometer/trip odometer switch button.
3. While still holding the odometer/trip odometer switch button depressed, turn the ignition switch to the ON position, but do not start the engine.
4. Release the odometer/trip odometer switch button.
5. The instrument cluster will simultaneously begin to illuminate all of the operational segments in the VFD units, and perform a bulb check of each operational LED indicator. The VFD segments and LED indicators remain illuminated as each gauge needle is swept to several calibration points and back. If a VFD segment or an LED indicator fails to illuminate, or if a gauge needle fails to sweep through the calibration points and back during this test, the instrument cluster must be replaced.
6. The actuator test is now completed. The instrument cluster will automatically exit the self-diagnostic mode and return to normal operation at the completion of the test. The actuator test will be aborted if the ignition switch is turned to the OFF position, or if an electronic vehicle speed message indicating that the vehicle is moving is received over the CAN data bus during the test.
7. Go back to STEP 1 to repeat the test, if necessary
 
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I just verified that this works on an early JK.. hell it worked on my 99 TJ. Here is your first step.
 
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