Toyota Avalon (XX50): Open Circuit in Main Relay 1 (C1311,C1312)

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual / Brake / Brake Control / Dynamic Control Systems / Electronically Controlled Brake System(for Hv Model) / Open Circuit in Main Relay 1 (C1311,C1312)

DESCRIPTION

The main relay supplies power to the switching solenoid and the linear solenoid.

The main relay remains on for approximately 2 minutes after the power switch is turned off and the input of brake pedal operation signals stops, and supplies power to the system to keep it ready to operate.

DTC No.

Detection Item

INF Code

DTC Detection Condition

Trouble Area

MIL

Note

C1311

Open Circuit in Main Relay 1

1

Either of the following is detected:

  • When the power switch is on (READY):

    The BS terminal voltage is less than 3.5 V for 0.05 seconds or more, when the IG1 terminal voltage is 9.5 V or more and operation of the main relay is requested.

  • When the power switch is off:

    The BS terminal voltage is less than 3.5 V for 0.05 seconds or more, when operation of the main relay is requested.
  • Open or short in main relay circuit
  • Skid control ECU (brake booster with master cylinder assembly)

Comes on
  • INF Code 1: SAE Code C12FA
  • Electronically controlled brake system DTC

C1312

Short Circuit in Main Relay 1

2

The BS terminal voltage is 3.5 V or more for 4.5 seconds or more, when operation of the main relay is requested.
  • Short in main relay circuit
  • Main relay internal stuck
  • Skid control ECU (brake booster with master cylinder assembly)

Comes on
  • INF Code 2: SAE Code C12FB
  • Electronically controlled brake system DTC

MONITOR DESCRIPTION

The skid control ECU (brake booster with master cylinder assembly) monitors the voltage at BS terminal.

When the main relay is instructed to be on and the voltage at BS terminal is within the range of an open circuit malfunction (voltage is practically equal to that when off), or when the main relay is instructed to be off and the voltage of the BS terminal is within the range of a short circuit malfunction (voltage is practically equal to that when on), an open circuit or short circuit is judged respectively and the MIL is illuminated and stores a DTC.

MONITOR STRATEGY

Related DTCs

C12FA: Main relay circuit low

C12FB: Main relay circuit high

Required Sensors/Components(Main)

Skid control ECU (brake booster with master cylinder assembly)

Required Sensors/Components(Related)

Skid control ECU (brake booster with master cylinder assembly)

Frequency of Operation

Continuous: C12FA (Case 1) and C12FB (Case 1)

During initial checking: C12FA (Case 2) and C12FB (Case 2)

Duration

0.054 seconds: C12FA (Case 1)

0.2 seconds: C12FA (Case 2)

2 seconds: C12FB (Case 2)

4.5 seconds: C12FB (Case 1)

MIL Operation

Immediately

Sequence of Operation

None

TYPICAL ENABLING CONDITIONS

C12FA (Case 1)

Monitor runs whenever the following DTCs are not stored

None

All of the following conditions are met

A, B and C

A. Skid control ECU (brake booster with master cylinder assembly) state

Normal

B. Command to main relay

On

C. Either of the following conditions is met

a or b

a. Both of the following conditions are met

-

Power switch

Off

Brake system voltage 1 (VM1)

Higher than 6.92 V

b. All of the following conditions are met

-

Power switch

On (READY)

Brake system voltage 1 (VM1)

Higher than 6.92 V

IG1 voltage

Higher than 9.54 V
C12FA (Case 2)

Monitor runs whenever the following DTCs are not stored

None

All of the following conditions are met

-

Skid control ECU (brake booster with master cylinder assembly) state

Initial check

Command to main relay

On

Brake system voltage 1 (VM1)

Higher than 6.92 V
C12FB (Case 1)

Monitor runs whenever the following DTCs are not stored

None

Both of the following conditions are met

-

Skid control ECU (brake booster with master cylinder assembly) state

Normal

Command to main relay

Off
C12FB (Case 2)

Monitor runs whenever the following DTCs are not stored

None

Both of the following conditions are met

-

Skid control ECU (brake booster with master cylinder assembly) state

Initial check

Command to main relay

Off

TYPICAL MALFUNCTION THRESHOLDS

C12FA (Case 1 and 2)

Power supply for linear solenoid

Less than 3.5 V
C12FB (Case 1 and 2)

Power supply for linear solenoid

3.5 V or more

COMPONENT OPERATING RANGE

C12FA

All of the following conditions are met

-

Skid control ECU (brake booster with master cylinder assembly) state

Normal

Command to main relay

On

Brake system voltage 1 (VM1)

Higher than 6.92 V

Power supply for linear solenoid

3.5 V or more
C12FB (Case 1)

All of the following conditions are met

-

Skid control ECU (brake booster with master cylinder assembly) state

Normal

Command to main relay

Off

Power supply for linear solenoid

Less than 3.5 V
C12FB (Case 2)

All of the following conditions are met

-

Skid control ECU (brake booster with master cylinder assembly) state

Initial check

Command to main relay

Off

Power supply for linear solenoid

Less than 3.5 V

CONFIRMATION DRIVING PATTERN

  1. Connect the Techstream to the DLC3.
  2. Turn the power switch on (IG).
  3. Turn the Techstream on.
  4. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
  5. Turn the power switch off.
  6. Turn the power switch on (IG).
  7. Turn the Techstream on.
  8. Wait 4.5 seconds.
  9. Enter the following menus: Chassis / ABS/VSC/TRAC / Trouble Codes.
  10. Read the DTCs.

    HINT:

    • If a DTC is output, the system is malfunctioning.
    • If a DTC is not output, perform the following procedure.
  11. If the DTCs are not output, perform a universal trip and check for permanent DTCs.

    Click here

    HINT:

    • If a permanent DTC is output, the system is malfunctioning.
    • If no permanent DTCs are output, the system is normal.

WIRING DIAGRAM

Refer to DTC C1241.

Click here

CAUTION / NOTICE / HINT

NOTICE:

  • After replacing the brake booster with master cylinder assembly, perform linear solenoid valve offset learning, ABS holding solenoid valve learning, yaw rate and acceleration sensor zero point calibration and system information memorization after performing "Reset Memory".

    Click here

  • Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

1.

PERFORM ACTIVE TEST USING TECHSTREAM (MAIN RELAY)

(a) Select the Active Test on the Techstream.

Click here

Chassis > ABS/VSC/TRAC > Active Test

Tester Display

Measurement Item

Control Range

Diagnostic Note

ECB Main Relay

Main relay

Relay ON/OFF

ECB: Electronically Controlled Brake System
Chassis > ABS/VSC/TRAC > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

ECB Main Relay

Main relay operation request

ON or OFF

ON: Relay on

OFF: Relay off

ECB: Electronically Controlled Brake System
Chassis > ABS/VSC/TRAC > Active Test

Active Test Display

ECB Main Relay

Data List Display

ECB Main Relay

(b) Check that the condition of the main relay observed on the Techstream changes according to Techstream operation.

Result

Proceed to

Main relay in the Data List turns ON/OFF using the Active Test.

A

Main relay in the Data List does not change using the Active Test.

B
B

GO TO STEP 4

A

2.

CHECK HARNESS AND CONNECTOR (BS TERMINAL)

(a) Turn the power switch off.

*a

Front view of wire harness connector

(to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

(b) Make sure that there is no looseness at the locking part and the connecting part of the connector.

OK:

The connector is securely connected.

(c) Disconnect the A35 skid control ECU (brake booster with master cylinder assembly) connector.

(d) Check both the connector case and the terminals for deformation and corrosion.

OK:

No deformation or corrosion.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A35-52 (BS) - Body ground

Always

11 to 14 V
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (BS CIRCUIT)
OK

3.

RECONFIRM DTC

(a) Reconnect the A35 skid control ECU (brake booster with master cylinder assembly) connector.

(b) Clear the DTCs.

Click here

Chassis > ABS/VSC/TRAC > Clear DTCs

(c) Turn the power switch off.

(d) Turn the power switch on (IG).

(e) Check if the same DTC is output.

Click here

Chassis > ABS/VSC/TRAC > Trouble Codes

Result

Proceed to

DTCs C1311 and C1312 are not output.

A

DTCs C1311 and/or C1312 are output.

B
A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

4.

CHECK HARNESS AND CONNECTOR (+BI TERMINAL)

(a) Turn the power switch off.

*a

Front view of wire harness connector

(to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

(b) Make sure that there is no looseness at the locking part and the connecting part of the connector.

OK:

The connector is securely connected.

(c) Disconnect the A35 skid control ECU (brake booster with master cylinder assembly) connector.

(d) Check both the connector case and the terminals for deformation and corrosion.

OK:

No deformation or corrosion.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A35-15 (+BI1) - Body ground

Always

11 to 14 V

A35-5 (+BI2) - Body ground

Always

11 to 14 V
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (+BI CIRCUIT)
OK

5.

CHECK HARNESS AND CONNECTOR (BS TERMINAL)

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A35-52 (BS) - Body ground

Always

11 to 14 V

*a

Front view of wire harness connector

(to Skid Control ECU (Brake Booster with Master Cylinder Assembly))
OK

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (BS CIRCUIT)

Skid Control ECU Malfunction (C1300)

Linear Solenoid Valve Offset Learning undone (C1345,C1368). Pressure Holding Solenoid Valve Learning Undone (C1349,C134A). Increasing Pressure Solenoid (FR) (C1352-C1359)

See More:

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Toyota Avalon (XX50) 2019-2022 Service & Repair Manual

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