How To… Find The Road Speed Signal on Newer Vehicles.

How To… Find The Road Speed Signal on Newer Vehicles.

On some newer vehicles the roadspeed governor is controlled by the CAN bus system. On these systems the road speed information is sent from the ABS computer to the main ECU using the CAN bus system.

With that said we have found several new vehicles that has CAN Bus and ABS but the roadspeed governor is NOT controlled by the CAN Bus system. So don’t automatically assume that the road speed on newer vehicles equiped with CAN Bus and ABS system use the newer CAN Bus techenology to control the road speed.

Steps to find out if the vehicle is getting the signals form the ABS system:

Step 1 – Remove the ABS fuses. (It normally has 2).
Step 2 – Drive the vehicle and see if it still has a road speed governor.
Step 3 – If it still has a road speed governor with the fuses removed try completely disconnecting the ABS ECU connector.
Step 4 – If the car has a lowered rev limiter in all gears with the fuses removed or ABS disconnected it is a CAN bus type 
Step 5 – If the road speed limit disappears with the fuses removed or ABS disconnected  it is a CAN bus type 
Step 6 – If the road speed signal is a CAN bus type then find the schematic and tie into the CAN bus system.
Step 7 – If the schematic doesn’t exist you probably will not be able to remove the road speed limit unless or until the code has been developed for the particular vehicle, Contact us to check. 
Step 8 – If it still has a road speed limiter your vehicle don’t use the ABS signal to control the road speed.

In the vehicle don’t use the ABS control unit to control the road speed then follow these steps:

Step 1 – Find the normal road speed signal.
Step 2 – View the road speed signal with a oscilloscope.
Step 3 – If it is a square-wave it is a probably a HALL type sensor.
Step 4 – If it is a  sine-wave it is probably a Magnetic ( inductive) type sensor.
Step 5 – Clamp the road speed like normal with the Unichip.