ANTI-LOCK BRAKE SYSTEM, Diagnostic DTC:C1271, C1272, C1401, C1402

DESCRIPTION

• for 4WD and Pre-Runner:

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

  Skid control 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 (brake actuator assembly).

  Tech Tips

  When the connectors between the speed sensor and skid control ECU (brake actuator assembly) are connected, the following waveform is output.

  

  *1	Speed Sensor	*2	Skid Control Rotor
  *a	Waveform (Reference): Between Speed Sensor (-) and Body Ground	*b	Low speed
  *c	High speed	-	-

• for 2WD other than Pre-Runner:

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

  The speed sensor generates vehicle speed pulses based on the rotation of the skid control rotor. The skid control ECU (brake actuator assembly) detects the speed of each wheel using this vehicle speed pulse.

  Tech Tips

  When the connectors between the speed sensor and skid control ECU (brake actuator assembly) are connected, the following waveform is output.

  

  *1	Speed Sensor	*2	Skid Control Rotor
  *a	Waveform (Reference): Between Speed Sensor (-) and Body Ground	*b	Low speed
  *c	High speed	-	-

• *1: for 4WD and Pre-Runner

• *2: for 2WD other than Pre-Runner

PROCEDURE

1. CHECK FRONT SPEED SENSOR INSTALLATION

   
   

   1. Turn the ignition switch off.

   2. 

      *a	Normal
      *b	Abnormal
      *c	Clearance

      Check the speed sensor installation.

      for 2WD other than Pre-Runner: Click here

      for 4WD and Pre-Runner: Click here

      OK
      There is no clearance between the sensor and the front steering knuckle.
      The installation bolt is tightened properly.

      Result
      Proceed to OK NG

   
   

   NG

   INSTALL FRONT SPEED SENSOR CORRECTLY for 2WD other than Pre-Runner: Click here INSTALL FRONT SPEED SENSOR CORRECTLY for 4WD and Pre-Runner: Click here

   OK

2. INSPECT FRONT SPEED SENSOR TIP

   
   

   1. Remove the front speed sensor.

      for 2WD other than Pre-Runner: Click here

      for 4WD and Pre-Runner: Click here

   2. Check the speed sensor tip.

      OK
      No scratches, oil, or foreign matter on the sensor tip.

      Note

      
      

      • If no damage to the speed sensor tip is found during this inspection, do not replace the speed sensor.

      • If there is iron powder sticking to the rotor, this will result in a malfunction, so confirm that the rotor is not contaminated with foreign material before replacing the sensor.

      • Check the speed sensor signal after cleaning or replacement.

        Click here

      Result
      Proceed to OK (for 4WD and Pre-Runner) OK (for 2WD other than Pre-Runner) NG

   
   

   OK (for 2WD other than Pre-Runner)

   INSPECT FRONT SKID CONTROL ROTOR Click here

   NG

   CLEAN OR REPLACE FRONT SPEED SENSOR

   OK (for 4WD and Pre-Runner)

3. INSPECT FRONT AXLE HUB INNER BEARING

   
   

   1. Remove the front axle hub inner bearing.

      Click here

   2. Check the front skid control rotor.

      OK
      No scratches, oil, or foreign matter on the rotors.

      Note

      Check the speed sensor signal after cleaning or replacement.

      Click here

      Tech Tips

      
      

      • The front skid control rotor is incorporated into the front axle hub inner bearing.

      • If the skid control rotor needs to be replaced, replace it together with the front axle hub inner bearing.

   3. Reinstall the front speed sensor and the front axle hub inner bearing.

      for the front speed sensor: Click here

      for the front axle hub inner bearing: Click here

      Result
      Proceed to OK NG

   
   

   OK

   GO TO STEP 5 Click here

   NG

   CLEAN OR REPLACE FRONT AXLE HUB INNER BEARING

4. INSPECT FRONT SKID CONTROL ROTOR

   
   

   1. Remove the front skid control rotor.

      Click here

   2. Check the front skid control rotor.

      OK
      No scratches, oil, or foreign matter on the rotors.

      Note

      Check the speed sensor signal after cleaning or replacement.

      Click here

   3. Reinstall the front speed sensor and the front skid control rotor.

      for the front speed sensor: Click here

      for the front skid control rotor: Click here

      Result
      Proceed to OK NG

   
   

   NG

   CLEAN OR REPLACE FRONT SKID CONTROL ROTOR

   OK

5. READ VALUE USING GTS (FRONT SPEED SENSOR)

   
   

   1. Connect the GTS to the DLC3.

   2. Start the engine.

   3. Turn the GTS on.

   4. Enter the following menus: Chassis / ABS/VSC/TRC / Data List.

   5. According to the display on the GTS, read the Data List.

      
      Chassis > ABS/VSC/TRC > Data List

      Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
      FR Wheel Speed	Front wheel speed sensor RH reading	Min.: 0 km/h (0 mph) Max.: 326.4 km/h (202 mph)	Vehicle stopped: 0 km/h (0 mph)	When driving at constant speed: No large fluctuations
      FL Wheel Speed	Front wheel speed sensor LH reading	Min.: 0 km/h (0 mph) Max.: 326.4 km/h (202 mph)	Vehicle stopped: 0 km/h (0 mph)	When driving at constant speed: No large fluctuations

      
      Chassis > ABS/VSC/TRC > Data List

      Tester Display
      FR Wheel Speed
      FL Wheel Speed

   6. Check that there is no difference between the speed value output from the speed sensor displayed on the GTS and the speed value displayed on the speedometer when driving the vehicle.

      Tech Tips

      Factors that affect the indicated vehicle speed include tire size, tire inflation and tire wear. The speed indicated on the speedometer has an allowable margin of error. This can be tested using a speedometer tester (calibrated chassis dynamometer). For details about testing and the margin of error, see the reference chart.

      Click here

      OK
      The speed value output from the speed sensor displayed on the GTS is the same as the actual vehicle speed measured using a speedometer tester (calibrated chassis dynamometer).

      Tech Tips

      If troubleshooting has been carried out according to the Problem Symptoms Table, refer back to the table and proceed to the next step.

      Click here

      Result
      Proceed to OK NG

   
   

   OK

   USE SIMULATION METHOD TO CHECK Click here

   NG

6. REPLACE FRONT SPEED SENSOR

   
   

   1. Turn the ignition switch off.

   2. Replace the front speed sensor.

      for 2WD other than Pre-Runner: Click here

      for 4WD and Pre-Runner: Click here

      Note

      Check the speed sensor signal after replacement.

      Click here

      Result
      Proceed to NEXT

   
   

   NEXT

7. RECONFIRM DTC

   
   

   1. Clear the DTCs.

      Click here

      
      Chassis > ABS/VSC/TRC > Clear DTCs

   2. Turn the ignition switch off.

   3. Start the engine.

   4. Drive the vehicle at a speed of 40 km/h (25 mph) or more for at least 60 seconds.

   5. Check if the same DTC is recorded.

      Click here

      
      Chassis > ABS/VSC/TRC > Trouble Codes

      Result
      Result Proceed to DTCs C1401 and C1402 are not output A DTCs C1401 and/or C1402 are output (for 4WD and Pre-Runner) B DTCs C1401 and/or C1402 are output (for 2WD other than Pre-Runner) C

      Note

      Check the speed sensor signal after replacement.

      Click here

      Tech Tips

      for 4WD and Pre-Runner:

      
      

      • The front skid control rotor is incorporated into the front axle hub inner bearing.

      • If the front skid control rotor needs to be replaced, replace it together with the front axle hub inner bearing.

   
   

   A

   END

   B

   REPLACE FRONT AXLE HUB INNER BEARING Click here

   C

   REPLACE FRONT SKID CONTROL ROTOR Click here