Section 10 ABS DIAGNOSIS - Testroete

1 toyota Brake Systems - Course 552143 The ABS ECU has a self-diagnostic system which monitors the inputand output circuits. The ABS ECU operates the solenoid valves and thepump motor in sequence in order to check each respective electricalsystem. This function operates only once each time the ignition switchis turned ON. On some earlier models it operates when the vehicle istraveling at a speed greater than 4 mph with the stop light (brakelight) switch OFF. During this check the operation of the actuator canbe heard, however this is normal and does not indicate a Check FunctionThe check function mayvary depending on thenumber of RH Pressure Holding ValveFront RH Pressure Reduction ValveFront LH Pressure Holding ValveFront LH Pressure Reduction ValveRear RH Pressure Holding ValveRear RH Pressure Reduction ValveRear LH Pressure Holding ValveRear LH Pressure Reduction ValvePump MotorWhen a problem is detected in any of the signal systems, the ECUturns on the ABS warning light in the combination meter to alert thedriver that a malfunction has occurred.

2 The code is stored in memoryfor access at a later time. Diagnostic trouble codes can be read from theWarning light. The ABS ECU will also store the diagnostic troublecodes for any ABS Warning LightThe light warns the driverof an ABS 10 ABS DIAGNOSISD iagnosis andTroubleshootingDiagnostic FunctionSection 10144 toyota Technical TrainingTo access the diagnostic trouble codes stored in the ECU, locate the DataLink Connector (DLC1) or (DLC2). Consult the Repair Manual or theABS Reference Card to determine whether the ABS Check Connector isphysically disconnected or the short pin for Wa and Wb is access diagnostic codes: Disconnect the check connector or remove the short pin in DLC1.

3 Jumper terminals Tc and E1 of the Data Link Connector (DLC1 orDLC2). Turn the ignition switch ON and read the trouble code from theABS warning light on the Combination and Avalon w/Bosch ABS, no Short Pin. Jumper Tc and Code CheckTo access diagnosticcodes, remove the shortpin, jumper Tc and E1in DLC1 and turn theignition switch the computer has not detected a malfunction, the lamp will blink twotimes per second after a two second pause. When a malfunction hasbeen detected there will be a 4 second pause, then the first digit willbegin. The number of times the lamp blinks before a one and a halfsecond pause is the first digit of the code. Next, the number of blinksbefore the second pause is the second digit of the code.

4 In the examplebelow, the first code is Code 11 and the second code is there is more than one trouble code, the code with the smallest numberwill appear first, followed by a pause for seconds, then the next codeDiagnostic CodesA normal code (steadyflashing trouble light)is output when there is nofault found. If more thanone fault is detected,each code is Code CheckNOTED iagnostic CodesABS DiagnosisToyota Brake Systems - Course 552145will appear in the same manner as described earlier. Finally, the entireprocedure will be repeated after a four second chart below identifies each code and reveals the circuit orcomponent which requires further DIAGNOSIS . The total number ofdiagnostic codes may vary between vehicles so it is important to referto the Repair Manual for the specific vehicle you are Warning LightBlinking Pattern Diagnosis11 ONOFFBE3831 Open circuit in ABS control (solenoid) relay circuit12 ONOFFBE3831 Short circuit in ABS control (solenoid) relay circuit13 ONOFFBE3831 Open circuit in ABS control (motor) relay circuit14 ONOFFBE3831 Short circuit in ABS control (motor)

5 Relay circuit21 ONOFFBE3832 Open or short circuit in 3-position solenoid circuit forright front wheel22 ONOFFBE3832 Open or short circuit in 3-position solenoid circuit forleft front wheel23 ONOFFBE3832 Open or short circuit in 3-position solenoid circuit forright rear wheel24 ONOFFBE3832 Open or short circuit in 3-position solenoid circuit forleft rear wheel31 ONOFFBE3833 Right front wheel speed sensor signal malfunction32 ONOFFBE3833 Left front wheel speed sensor signal malfunction33 ONOFFBE3833 Right rear wheel speed sensor signal malfunction34 ONOFFBE3832 Left rear wheel speed sensor signal malfunction35 ONOFFBE3833 Open circuit in left front or right rear speed sensorcircuit36 ONOFFBE3833 Open circuit in right front or left rear speed sensorcircuit37 ONOFFBE3833 Faulty rear speed sensor rotor41 ONOFFBE3834 Low battery positive voltage or abnormally

6 Highbattery positive voltage51 ONOFFBE3836 Pump motor is lockedOpen in pump motor groundAlwaysonONOFF Malfunction in ECUT rouble Code ChartThe code identifies thecomponent or circuit whichrequires further 10146 toyota Technical TrainingThe Repair Manual takes the DIAGNOSIS several steps further inproviding a circuit inspection and inspection procedure for eachdiagnostic code. It provides a circuit description as well as theparameters under which the code was set for each stored code. Awiring diagram schematic of the electrical circuit is also provided forready Descriptionand Wiring DiagramA circuit descriptionincludes the parametersfor setting the InspectionABS DiagnosisToyota Brake Systems - Course 552147An inspection procedure follows the circuit inspection withcomponents, connectors, pin locations and measurement values todiagnose the circuit.

7 Each step is outlined in sequence, leading to ProcedureThe inspection procedureincludes components,connectors and pinlocations as well asmeasurement values todiagnose the 10148 toyota Technical TrainingFollowing DIAGNOSIS and repair, clear the trouble codes stored in theECU. The procedure will vary depending on the model and year. Eitherrefer to the ABS Reference Card or Repair Manual for specifics. Theessential difference is in disconnecting the actuator check connector onearlier models as compared to the removal of the short pin connector inthe DLC1 or DLC2 connector. A typical procedure is outlined below: Jumper terminals Tc and E1 of the DLC2 or DLC1 and remove theshort pin from DLC1.

8 Turn ignition switch ON. Depress the brake pedal 8 or more times within 3 seconds. Check that the warning light shows the normal code. Remove the jumper wire and reinstall the short ensure that the brake light switch opens and closes each time, allowthe brake pedal to return to the full up position each time when clearingcodes. If the code does not clear, the ignition switch must be cycled OFFthen ON before depressing the brake pedal 8 times in 3 DiagnosticTrouble CodesDiagnostic TroubleCode ClearanceABS DiagnosisToyota Brake Systems - Course 552149 Eight additional diagnostic codes (71 through 78) are available totrouble-shoot the speed sensors and rotors. They determine whetherthe signal to the ECU is a low output voltage or an abnormal change inoutput voltage.

9 When using the signal check, make sure that thevehicle is driven straight ECU is placed in signal check mode differently based on model andyear, so again it is important to have the appropriate repair manualavailable. In some early models, the parking brake in conjunction withthe service brake were used to enter this most cases, connect terminals Tc and E1 at DLC1 prior to drivingthe vehicle. To read the code: Connect terminals Ts and E1 (Tc and E1 remain connected). In earlier models the actuator check connector was disconnected. Code No. DIAGNOSIS Trouble Area 71 Low output voltage of right front speed sensor Right front speed sensor Sensor installation 72 Low output voltage of left front speed sensor Left front speed sensor Sensor installation 73 Low output voltage of right rear speed sensor Right rear speed sensor Sensor installation 74

10 Low output voltage of left rear speed sensor Left rear speed sensor Sensor installation 75 Abnormal change in output voltage of right front speed sensor Right front speed sensor rotor 76 Abnormal change in output voltage of left front speed sensor Left front speed sensor rotor 77 Abnormal change in output voltage of right rear speed sensor Right rear speed sensor rotor 78 Abnormal change in output voltage of left rear speed sensor Left rear speed sensor rotorSpeed SensorSignal CheckDiagnostic TroubleCodes forSpeed SensorCheck FunctionConsult the Repair Manualfor specific instructions toplace the ECU into thediagnostic mode and toread the 10150 toyota Technical TrainingThe deceleration sensor can be checked both statically anddynamically.