Speed Limiter Upgrade/Hack

January 19

My Auris icon didn't come with cruise control and speed limit features as standard. There is plenty of information on upgrading to a cruise control stalk. However, i could find no information on enabling the speed limiting feature.

The speed limiter is just an extra switch on the steering wheel which has been faceplate blanked off (on this model). This feature would be really handy with the 20mph speed zones popping up everywhere, as it defaults to 20mph when activated.

Of course you could find a suitable used replacement steering wheel from a higher spec model with the speed limiter button. Then replace the switch panels or the whole steering wheel. However its another £50-£100, and finding the right wheel for your car model. Whereas a switch and wire costs pennies, and is the greener solution.

The upgraded car is a 2016 auris mk2 e180 1.2 turbo cvt, model NRE 185. I obtained wiring info for this car from Toyota. WIring is likely to be same for other mark 1 & 2 auris models and Corollas of this era, but dont quote me on that. Do this upgrade at your own risk!

Steps:

1. Disconnect the negative Battery terminal.

2. Remove steering wheel airbag module.
This can be a rather frustrating experience. Do the right clip first (remove cruise panel to see what your doing) then do left, then pull out from the bottom. The left and right spring contacts can be rather stiff, and need to be pressed to release airbag. No need to disconnect airbag connector, just rest it above wheel. See airbag picture to help you see how it clips in.

3. Clean horn contacts (bonus step)
Whilst the airbag is out, sandpaper/wirewool clean your four brass horn contacts and airbag side contacts. These can oxidize with age and can make using the horn a rather forceful operation. Lightly smear with electrical contact grease/oil to avoid any future oxidation.

4. Mount the switch
Putting the switch on the front of the steering wheel would be an eyesore. I mounted my tactile switch behind the right paddle shift control using a double sided sticky pad (temporary fit). Easy to locate by touch, but out of sight. Anywhere else on on the rear of your moving steering wheel is good. The switch should be a "non-latching push-to-make" type switch. I used a simple low profile tactile button switch often found mounted on pcb boards.

5. Tap in the new speed limiter switch.
You will need to tap into two wires running from the black 12 pin connector running to the right switch panel.

The black connector on this model was fully wired with 12 wires (6x2).
Looking at rear of terminal (wire side), pins are numbered;

Top : wire side
6 5 4 3 2 1
12 11 10 9 8 7
Bottom : wire side

7: black: common switch ground
9: red: speed limit signal

If your connector is not fully wired, to these pins, you may be able to improvise a connection to these pins on the rear of the connector (eg wedge a solid core wire snug in hole). A much easier job!

If its already pre-wired, cut back the black shroud to ease access. Strip/scrape back the two wires in situ (avoid cutting wires), solder the tap wires leading to the switch and insulate.

6. Fit cruise stalk
If you dont already have a cruise stalk, fit it now. Its cheap to buy, about £10 new on eBay.

7. Test feature
Plug all connectors back in. Test it by switching the ignition on and pressing the button. Speed limit symbol settings should now appear on dash. The speed limit figure will appear on toggling the cruise stalk up or down.

Job done.