Lexus ES: 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:
|
| Comes on |
|
| 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. |
| Comes on |
|
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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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
- Connect the Techstream to the DLC3.
- Turn the power switch on (IG).
- Turn the Techstream on.
- Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
- Turn the power switch off.
- Turn the power switch on (IG).
- Turn the Techstream on.
- Wait 4.5 seconds.
- Enter the following menus: Chassis / ABS/VSC/TRAC / Trouble Codes.
-
Read the DTCs.
HINT:
- If a DTC is output, the system is malfunctioning.
- If a DTC is not output, perform the following procedure.
-
If the DTCs are not output, perform a universal trip and check for permanent DTCs.
Click here
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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
| Tester Display | Measurement Item | Control Range | Diagnostic Note |
|---|---|---|---|
| ECB Main Relay | Main relay | Relay ON/OFF | ECB: Electronically Controlled Brake System |
| 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 |
| 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 |
|
| 2. | CHECK HARNESS AND CONNECTOR (BS TERMINAL) |
| (a) Turn the power switch off. |
|
(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 A45 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 |
|---|---|---|
| A45-52 (BS) - Body ground | Always | 11 to 14 V |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR (BS CIRCUIT) |
|
| 3. | RECONFIRM DTC |
(a) Reconnect the A45 skid control ECU (brake booster with master cylinder assembly) connector.
(b) Clear the DTCs.
Click here
(c) Turn the power switch off.
(d) Turn the power switch on (IG).
(e) Check if the same DTC is output.
Click here
| 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. |
|
(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 A45 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 |
|---|---|---|
| A45-15 (+BI1) - Body ground | Always | 11 to 14 V |
| A45-5 (+BI2) - Body ground | Always | 11 to 14 V |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR (+BI CIRCUIT) |
|
| 5. | CHECK HARNESS AND CONNECTOR (BS TERMINAL) |
| (a) Measure the voltage according to the value(s) in the table below. Standard Voltage:
|
|
| OK | | REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR (BS CIRCUIT) |
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