DTC C1401: Front Speed Sensor RH Malfunction; DTC C1402: Front Speed Sensor LH Malfunction: Description

WARNING: This page is about a different car, the 2009 Lexus IS 350 and 2009 Lexus IS 250. However, it is still accessible from the selected car via links, so may be relevant.

The speed sensor detects the wheel speed and sends the appropriate signals to the skid control ECU. These signals are used for the ABS control system. This speed sensor contains a sensor IC, which consists of 2 MREs (Magnetic Resistance Elements). The speed sensor rotor, which consists of 48 sets of N and S poles arranged in a circle, is integrated with the inner race of the hub bearing.

To detect the rotation direction, the output waves are used to determine the relationship of the pulses that are generated by the 2 MREs. Upon receiving this signal, the sensor IC outputs a forward or backward waveform to the ECU.

Fig 1: Speed Sensor Circuit Diagram & Signal Pulse Graph

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

DTC Code	DTC Detection Condition	Trouble Area
C1401 C1402	Any of the following is detected: At a vehicle speed 10 km/h (6 mph) or more, output voltage from one of the speed sensors is less than that from the other sensors for 15 seconds or more (for 2WD) or for 30 seconds or more (for 4WD). At a vehicle speed less than 10 km/h (6 mph), output from one of the speed sensors is 0 km/h (0 mph) for 1 second or more. At a vehicle speed 10 km/h (6 mph) or more, outputs from both front speed sensors are 0 km/h (0 mph) for 15 seconds or more (for 2WD) or for 30 seconds or more (for 4WD).	Front speed sensor RH/LH Speed sensor rotor

HINT:

DTC C1401 is for the front speed sensor RH.
DTC C1402 is for the front speed sensor LH.