DTC C1281: Master Cylinder Pressure Sensor Output Malfunction (Test Mode DTC): Procedure

1. Check that the stop lights come on when the brake pedal is depressed, and go off when the brake pedal is released.

   OK

   Condition	Illumination Condition
   Brake pedal depressed	ON
   Brake pedal released	OFF

NG → See step   8 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Select the Data List on the Techstream. Refer to DATA LIST / ACTIVE TEST .
   ABS/VSC/TRAC
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Stop Light SW	Stop light switch / ON or OFF	ON: Brake pedal depressed OFF: Brake pedal released	-

4. Check that the stop light switch display observed on the Techstream changes according to brake pedal operation.

   OK

   The Techstream displays ON or OFF according to brake pedal operation.

NG → See step   5 

OK: Go to next step 

1. Select the Data List on the Techstream. Refer to DATA LIST / ACTIVE TEST .
   ABS/VSC/TRAC
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Master Cylinder Sensor	Master cylinder pressure sensor / min.: 0 V, max.: 5 V	When brake pedal is released: 0.3 to 0.9 V	Reading increases when brake pedal is depressed

2. Check that the brake fluid pressure value of the master cylinder pressure sensor observed on the Techstream changes when the brake pedal is depressed.

   OK

   When the pedal is depressed, voltage displayed on the Techstream increases.

NG → See step   7 

OK: Go to next step 

1. Turn the ignition switch off.
2. Perform the sensor check in the Test Mode procedure. Refer to TEST MODE PROCEDURE .

   OK

   All Test Mode DTCs are cleared.

NG → See step   7 

OK → See step   6 

1. Turn the ignition switch off.
   Fig 1: Identifying Skid Control ECU Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Make sure that there is no looseness at the locking part and the connecting part of the connector.
3. Disconnect the skid control ECU connector.
4. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   A66-2 (STP) - Body ground	Stop light switch ON (Brake pedal depressed)	8 to 14 V
   A66-2 (STP) - Body ground	Stop light switch OFF (Brake pedal released)	Below 1.5 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT) 

OK → See step   7