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 wheel speed and sends the appropriate signals to the skid control ECU. These signals are used for ABS 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 change and sends a pulse signal to the skid control ECU.

HINT:

When testing voltage, perform the test while the connector between the sensor and ECU is connected. Do not disconnect the connector between the sensor and ECU.

Fig 1: Identifying Speed Sensor Waveform

DTC Code	DTC Detection Condition	Trouble Area
C1401 C1402	Any of the following is detected: At a vehicle speed of 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. 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 of 10 km/h (6 mph) or more, outputs from both front speed sensors are 0 km/h (0 mph) for 15 seconds or more.	Front speed sensor RH/LH Speed sensor rotor Sensor installation
C1271 C1272	Detected only during Test Mode.	Front speed sensor RH/LH Speed sensor rotor Sensor installation

HINT:

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