How To – Unichip Road Speed Signals

How To… Unichip Road Speed Signals

How to revert back to the factory road speed signal on a Tacoma or FJ Cruiser

Sometimes we need to do some trouble shooting to isolate a specific problem or symptom, in this case the symptom might be related to the vehicle’s road speed or transmission shift points.

Road Speed Signals

Road-speed signals are normally  digital signals generated by the speed sensor in the transmission. It can also be inductive signals, or sometimes the ABS system will send road-speed information over the CAN bus to the ECU. The ECU uses the speed signal to calculate road speed and automatic transmission shift points. We use the Unichip to manipulate the road-speed signal  in order to remove road-speed limiter.

Almost all road-speed signals will be  variable frequency, which will increase as the road speed increases. We take road speed signal in and out of the Unichip to control the final signal send to the ECU, thus controlling shift points and road speed. Some vehicles with automatic transmissions will have two road speed signals to monitor gear box slippage.

In the example below the vehicle is using one digital signal to control the road speed. To get the vehicle back to stock we have to cut the output wire from the Unichip and join it back to the factory road speed signal. This way the road speed signal will not be manpulated by the Unichip, but the vehicle ECU will see the factory signal unmodified coming directly from the speed sensor located in the transmission.

Click on the images to enlarge

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Warning! Sometimes you have to remove both the road speed input and output signal from the Unichip

Tip! If you have a plug and play then the easiest would  be to just remove the Unichip plug and play which will revert the vehicle back to stock.