ELECTRONICALLY CONTROLLED BRAKE SYSTEM ABS Warning Light Remains ON

DESCRIPTION

The skid control ECU (brake booster with master cylinder assembly) is connected to the combination meter assembly via CAN communication.

If any of the following is detected, the ABS warning light remains on:

• The skid control ECU (brake booster with master cylinder assembly) connector is disconnected from the brake booster with master cylinder assembly.

• There is a malfunction in the skid control ECU (brake booster with master cylinder assembly) internal circuit.

• There is an open in the harness between the combination meter assembly and the skid control ECU (brake booster with master cylinder assembly).

• The ABS control system is defective.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

PROCEDURE

1. CHECK CAN COMMUNICATION SYSTEM

   
   

   1. Check if CAN communication system DTCs are output.

      
      

      • w/o Toyota Safety Sense Click here

      • w/ Toyota Safety Sense Click here

      Result

      Result	Proceed to
      DTC is not output.	A
      CAN communication system DTC is output. (w/o Toyota Safety Sense)	B
      CAN communication system DTC is output. (w/ Toyota Safety Sense)	C

   
   

   B

   INSPECT CAN COMMUNICATION SYSTEM Click here

   C

   INSPECT CAN COMMUNICATION SYSTEM Click here

   A

2. CHECK IF SKID CONTROL ECU CONNECTOR IS SECURELY CONNECTED

   
   

   1. Check if the skid control ECU (brake booster with master cylinder assembly) connector is securely connected.

      OK
      The connector is securely connected.

   
   

   NG

   CONNECT CONNECTOR TO ECU CORRECTLY

   OK

3. CHECK AUXILIARY BATTERY

   
   

   1. Check the auxiliary battery voltage.

      Standard Voltage
      Tester Connection Switch Condition Specified Condition Auxiliary battery Ignition switch ON (IG) 11 to 14 V Auxiliary battery Ignition switch ON (READY) 11 to 15.5 V

   
   

   NG

   CHARGE OR REPLACE AUXILIARY BATTERY

   OK

4. CHECK HARNESS AND CONNECTOR (IG1 TERMINAL)

   
   
   1. 

      Text in Illustration

      *a	Front view of wire harness connector (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      Disconnect the skid control ECU (brake booster with master cylinder assembly) connector.

   2. Turn the ignition switch to ON (IG).

   3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Switch Condition Specified Condition A29-16 (IG1) - Body ground Ignition switch ON (IG) 11 to 14 V

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR (IG1 CIRCUIT)

   OK

5. CHECK HARNESS AND CONNECTOR (GND TERMINAL)

   
   
   1. 

      Text in Illustration

      *a	Front view of wire harness connector (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      Turn the ignition switch off.

   2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition A29-28 (GND) - Body ground Always Below 1 Ω A29-27 (GND2) - Body ground Always Below 1 Ω A29-26 (GND3) - Body ground Always Below 1 Ω A29-25 (GND4) - Body ground Always Below 1 Ω A29-24 (GND5) - Body ground Always Below 1 Ω A29-23 (GND6) - Body ground Always Below 1 Ω

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR (GND CIRCUIT)

   OK

6. INSPECT COMBINATION METER ASSEMBLY

   
   

   1. Reconnect the skid control ECU (brake booster with master cylinder assembly) connector.

   2. Perform the Active Test of the combination meter assembly (meter CPU) using the GTS Click here.

   3. Check the combination meter assembly.

      OK
      The ABS warning light turns on or off in accordance with GTS operation.

      Result

      Result	Proceed to
      OK (for LHD)	A
      OK (for RHD)	B
      NG	C

      Tech Tips

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

   
   

   A

   REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY Click here

   B

   REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY Click here

   C

   REPLACE COMBINATION METER ASSEMBLY Click here