Best Speedometer Calibrator?

[BoomerBob]

On a recent road trip I noticed my GPS had a very different reading than the speedo. At 80 mph, a common cruising speed here in the Southwest, my speedo read 89. The difference gets worse the faster the speed. It's only 3-4 mph difference at 40.

Just wondering if there are any speedo calibrators that plug into the ODBII port to correct the reading. I'm running stock size 16" tires.

I've done the searches and found a link to something that gets spliced into the system but that's not what I'm looking for. A simple ECU programmer to recalibrate the speedo like other makes and models that plugs into the ODBII is what I'm hoping to find. If not I'll just live with it.

Yotatech had a couple of methods but they are both splice or unclear methods.

*Write Up* Installing the Yellow Box Speedo Calibrator - YotaTech Forums

Speed calibration after larger tires and regear? - YotaTech Forums

Speedometer correction - Toyota 120 Platforms Forum

 

[BoomerBob]

It occurred to me after posting this question that the speed reading doesn't go through the ECU so there may not be an ODBII port method to correct this. If not then I guess that answers my question. Toyota may have isolated this particular system for some reason during the 3rd gen years.

 

[jross20]

It occurred to me after posting this question that the speed reading doesn't go through the ECU so there may not be an ODBII port method to correct this. If not then I guess that answers my question. Toyota may have isolated this particular system for some reason during the 3rd gen years.

I need to know as well for my 2000, I want to make sure I can calibrate before I install my new tires.

 

[Bad Luck]

I'm not sure if this helps, but if you have an Ultra Gauge you can calibrate to adjust it for true distance and it will change the mph on the Ultra Gauge display.

 

[jross20]

I'm not sure if this helps, but if you have an Ultra Gauge you can calibrate to adjust it for true distance and it will change the mph on the Ultra Gauge display.

Does this calibrate the vehicle or just the ultra gauge?

 

[Bad Luck]

Does this calibrate the vehicle or just the ultra gauge?

Just the Ultra Gauge

 

[phattyduck]

Speedometer calibration cannot happen through the ECU/OBD-II port. Not only is the ECU not programmable, the speedometer SENDS the signal to the ECU, not the other way around.

On ABS equipped 3rd gen 4Runners (almost all of them), the system goes like this:
ABS wheel speed sensors -> ABS computer -> Gauge cluster -> ECU (and 4WD computer, diff lock ECU, etc.)

To calibrate the speedo (and the speed the ECU sees and reports via OBD-II), you need to interrupt the signal between the ABS computer and the gauge cluster and use a calibrator there.

I chose the Dakota Digital speedometer calibrator, and installed it in the passenger kick panel next to the ABS computer:

-Charlie

EDIT: Also note that gearing will have no effect on the speedometer, since the speed signal is taken from the wheels, not the transmission/transfer case output. Only tire rolling diameter will change the speedo reading.

 

[danwyl]

I think the only way to calibrate the speedometer manually is to change the tooth gearing in the speedometer itself. [MENTION=169804]turbodb[/MENTION] has a writeup for his tacoma that should work just as well for your 4runner. Speedometers, Odometers, and Gas Mileage - All Lies! | ADVENTURE TACO | Toyota Tacoma Build, Adventures, and Exploration

 

[phattyduck]

I think the only way to calibrate the speedometer manually is to change the tooth gearing in the speedometer itself. [MENTION=169804]turbodb[/MENTION] has a writeup for his tacoma that should work just as well for your 4runner. Speedometers, Odometers, and Gas Mileage - All Lies! | ADVENTURE TACO | Toyota Tacoma Build, Adventures, and Exploration

That is only true on the Tacoma and non-ABS 3rd gens. Even then, if it has the electric speedo sender on the transfer case / transmission, you can still use a digital calibrator between that and the gauge cluster...

-Charlie

 

[BoomerBob]

I'm not sure if this helps, but if you have an Ultra Gauge you can calibrate to adjust it for true distance and it will change the mph on the Ultra Gauge display.

I do run one of those. I guess I'll have to see if I can find how to do that.

Thanks everyone!

 

[WeakSauz]

Speedometer calibration cannot happen through the ECU/OBD-II port. Not only is the ECU not programmable, the speedometer SENDS the signal to the ECU, not the other way around.

On ABS equipped 3rd gen 4Runners (almost all of them), the system goes like this:
ABS wheel speed sensors -> ABS computer -> Gauge cluster -> ECU (and 4WD computer, diff lock ECU, etc.)

To calibrate the speedo (and the speed the ECU sees and reports via OBD-II), you need to interrupt the signal between the ABS computer and the gauge cluster and use a calibrator there.

I chose the Dakota Digital speedometer calibrator, and installed it in the passenger kick panel next to the ABS computer:

-Charlie

EDIT: Also note that gearing will have no effect on the speedometer, since the speed signal is taken from the wheels, not the transmission/transfer case output. Only tire rolling diameter will change the speedo reading.

+1 on this from Charlie.

I wired in the same unit and it works like a charm. It's great to know you can swap tire size to anything you want and re-calibrate

 

[BoomerBob]

Speedometer calibration cannot happen through the ECU/OBD-II port. Not only is the ECU not programmable, the speedometer SENDS the signal to the ECU, not the other way around.

On ABS equipped 3rd gen 4Runners (almost all of them), the system goes like this:
ABS wheel speed sensors -> ABS computer -> Gauge cluster -> ECU (and 4WD computer, diff lock ECU, etc.)

To calibrate the speedo (and the speed the ECU sees and reports via OBD-II), you need to interrupt the signal between the ABS computer and the gauge cluster and use a calibrator there.

I chose the Dakota Digital speedometer calibrator, and installed it in the passenger kick panel next to the ABS computer:
[/img]

-Charlie

EDIT: Also note that gearing will have no effect on the speedometer, since the speed signal is taken from the wheels, not the transmission/transfer case output. Only tire rolling diameter will change the speedo reading.

+1 on this from Charlie.

I wired in the same unit and it works like a charm. It's great to know you can swap tire size to anything you want and re-calibrate

Is there a step by step procedure somewhere on how to do this? Particularly which wires (colors) to splice into? I found this install manual for doing the calibrations.

Here's a source for them: Unusual Activity Detected - Free Shipping on Orders Over $99 at Summit Racing

 

[phattyduck]

Is there a step by step procedure somewhere on how to do this? Particularly which wires (colors) to splice into? I found this install manual for doing the calibrations.

Here's a source for them: Unusual Activity Detected - Free Shipping on Orders Over $99 at Summit Racing

Here it is from my build thread:

https://www.toyota-4runner.org/2456477-post12.html

-Charlie

 

[BoomerBob]

Here it is from my build thread:

https://www.toyota-4runner.org/2456477-post12.html

-Charlie

Perfect! Thanks!

 

[jross20]

Oh wow, so you basically add a "converter" box between the systems that converts the signal by applying a correction?

 

[WeakSauz]

Oh wow, so you basically add a "converter" box between the systems that converts the signal by applying a correction?

Yes. And you can adjust the calibration, too.

 

[BoomerBob]

UltraGauge Speed Calibration

I'm not sure if this helps, but if you have an Ultra Gauge you can calibrate to adjust it for true distance and it will change the mph on the Ultra Gauge display.

FWIW: I found this tutorial for matching the UG speed gauge with a GPS gauge. I figure the GPS is likely the most accurate we have easy access to. Add in a calculator most of us have on our smart phones and bob's your uncle.

How to calibrate distance using a GPS and a calculator:

NOTE
This distance calibration method is based on using GPS speed.
GPS speed is most accurate when driving in a straight line at a constant speed.

Step 1: Add a speed gauge (e.g. on page 1 zone 1 of the Ultragauge)
MENU Gauge/Page Menu .. Select Gauge/Page .. Select Gauges Select Page 1 Gauges
Use UP & DOWN keys to Navigate to MPH or KPH
Press MENU. This will cause the cursor to blink.
Pressing UP or DOWN change the number to 1
Press MENU to assign the Gauge to that Page 1 Zone 1.
Leave the menu by selecting Back, etc
The Ultragauge should now show the MPH or KPH on page 1
Step 2: Grab your calculator and your GPS navigation device, get in your car and head for the motorway.
Step 3: While driving at a constant high speed for at least a few seconds note down the speed readings of the Ultragauge and the GPS.
The readings are probably different.
Step 4: Find a convenient place to stop, switch on your calculator and do the following calculation: GPS speed reading divided by Ultragauge speed reading.
Step 5: Adjust the "Distance cal." factor in the Ultragauge
Menu - Vehicle Setup - Calibration - Calibrate Distance
Note the distance value shown by Ultragauge and on the calculator multiply this by the factor found in step 4
Press MENU and press UP or DOWN to adjust the distance value to the calculated value.
Press MENU to store the updated distance value. The Ultragauge now shows the new Distance cal. value
Leave the menu by selecting Back, etc
Switch off your calculator
Step 6: Take another drive on the motorway and check if the GPS speed reading and the Ultragauge speed reading at constant speed are now the same.
Step 7: If necessary make fine adjustments to the distance calibration value until GPS speed and Ultragauge speed are identical.

 

[phattyduck]

Oh wow, so you basically add a "converter" box between the systems that converts the signal by applying a correction?

Yeah, used all the time on motorcycles when swapping sprockets. Less often on trucks with gear ratio and tire size swaps.

-Charlie

 

[jross20]

Yeah, used all the time on motorcycles when swapping sprockets. Less often on trucks with gear ratio and tire size swaps.

-Charlie

Ahhh. Okay, so is the gold standard to use a gps to grab the speed? Basically how do I figure out how fast I am actually going so I can calibrate it...haha.

 

[phattyduck]

Ahhh. Okay, so is the gold standard to use a gps to grab the speed? Basically how do I figure out how fast I am actually going so I can calibrate it...haha.

I used phone GPS to verify, but I calculated what the correction factor should be based on tire size.

Original tire size: 225/75-15 = 28.29" diameter
New tire size: 265/70-17 = 31.61" diameter

31.61 / 28.29 = 1.117x or about 12% bigger. I applied a 12% correction using the calibrator, and the speedo read the same as it used to (67=65mph actual).

Speedometer generally read just a bit high (for legal reasons), so that's where I left it. Often, odometers (and OBD-II reported speed) is nearly perfectly accurate.

-Charlie