Circuit Description

The vehicle equipped with ABS detects a vehicle speed using the stability control ECU and wheel speed sensor. This sensor monitors a wheel rotation speed and sends the signal to the ECU.

The stability control ECU converts these wheel speed signals into a 4-pulse signal and outputs it to the ECM via the combination meter.

The ECM determines the vehicle speed based on the frequency of these pulse signals.

In the vehicle without ABS, the No. 1 vehicle speed sensor outputs a 4-pulse signal for every revolution of the rotor shaft, which is rotated by the transmission output shaft via the driven gear. After this signal is converted into a more precise rectangular waveform by the waveform shaping circuit inside the combination meter, it is then transmitted to the ECM. The ECM determines the vehicle speed based on the frequency of these pulse signals.

w/ ABS:

Fig 1: Vehicle Speed Sensor 'A' Mode W/ABS

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

w/ ABS:

Fig 2: Vehicle Speed Sensor 'A' Mode W/o ABS

Fig 3: DTC Table