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

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.

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?

Just the Ultra Gauge

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.

I think the only way to calibrate the speedometer manually is to change the tooth gearing in the speedometer itself. @turbodb 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

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

Thanks everyone!

+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

Here it is from my build thread:

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

-Charlie

Perfect! Thanks!

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