Toyota Corolla (E120) 2002–2008 Repair Manual / Diagnostics / Sfi system / Vehicle speed sensor ”a” / Circuit description
Toyota Corolla (E120): 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 signal.
W/ abs:
W/o abs:
Monitor description
Equipped with abs:
the ecm assumes that the vehicle is driven when the rpm of the transmission counter gear indicates more than 300 rpm and it has been over 30 seconds since the park/neutral position switch was turned off. If there is no signal from the vehicle speed sensor with these conditions satisfied, the ecm concludes that there is a fault in the vehicle speed sensor. The ecm will turn on the mil and a dtc is set.
Not equipped with abs:
the ecm assumes that the vehicle is driven when the park/neutral position switch is off and it has been over 4 seconds since the actual vehicle speed was 9 km/h or more.
If there is no signal from the vehicle speed sensor with these conditions satisfied, the ecm concludes that there is a fault in the vehicle speed sensor. The ecm will turn on the mil and a dtc is set.
Monitor strategy
Typical enabling conditions
Typical malfunction thresholds
Wiring diagram
Other materials:
Source voltage drop
The srs is equipped with a voltage–increase circuit (dc–dc converter) in the
airbag sensor assy center
in case the source voltage drops.
When the battery voltage drops, the voltage–increase circuit (dc–dc converter)
functions to increase the
voltage of the srs to normal voltage.
...
Circuit description
A thermistor is built in the engine coolant temperature sensor and changes
the resistance value according
to the engine coolant temperature.
The structure of the sensor and connection to the ecm is the same as those of
the intake air temperature
sensor.
Hint:
if the ecm detects the dtc ...
Inspection procedure
1 Inspect dlc3 terminal voltage
Turn the ignition switch to on.
measure voltage between terminals 13 (tc) and 4 (cg) of
dlc3.
Ok:
voltage: 10 – 16 v
2 Check harness and connector(between cruise control ecu assy
and dlc3)
Check for open and short circuit in harness ...