DTC C1401: Front Speed Sensor RH Malfunction; DTC C1271: Low Output Signal of Front Speed Sensor RH (Test Mode DTC); DTC C1272: Low Output Signal of Front Speed Sensor LH (Test Mode DTC); DTC C1402: Front Speed Sensor LH Malfunction: Description

The speed sensor detects the wheel speed and sends the appropriate signals to the skid control ECU. These signals are used for brake control.

Speed sensor rotors have rows of alternating N and S magnetic poles, and their magnetic fields change when the rotors turn.

Each speed sensor detects that magnetic field change and sends a pulse signal to the skid control ECU.

HINT: 

When the connectors between the speed sensor and skid control ECU are connected, the following waveform is output.

Fig 1: Speed Sensor Waveform Reference

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT: 

• DTCs C1401 and C1271 are for the front speed sensor RH.
• DTCs C1402 and C1272 are for the front speed sensor LH.