Code No.53: Motor
relay system (open circuit, short circuit or motor relay coil failure)
OPERATION
The motor relay 1 and the motor relay 2 are controlled by the ABS-ECU.
If the brake fluid pressure in the hydraulic brake booster (HBB) becomes low, the
ABS-ECU outputs the motor relay actuating signal to the motor relay 1 and the motor relay 2
and then the pump motor operates.
The ABS-ECU monitors the pump motor (at 49 terminal).
DIAGNOSIS CODE SET CONDITIONS
The diagnosis code is set if the motor relay circuit is open or short, the ABS-ECU internal
circuit malfunction occurs, or if the master cylinder and hydraulic unit assembly malfunction
of the hydraulic brake booster (HBB) occurs.
PROBABLE CAUSES
Malfunction of the motor relay 1 or the motor relay 2
Damaged wiring harness or connector
Malfunction of the ABS-ECU
Malfunction of the HBB (Master cylinder and hydraulic unit assembly)
DIAGNOSIS
STEP 1. Check the pump motor operation.
(1)Depress the pedal repeatedly more than 40 times until the pedal depressing force
feels heavy with the ignition switch at the "LOCK" (OFF) position.
(2)Turn the ignition switch to the "ON" position.
Q.
Does the pump motor operate?
Go to Step 23.
Go to Step 2.
STEP 2. Check the motor relay 1.
caution
Apply battery voltage according to the table below. Never confuse
the positive and negative battery terminals, or the diode inside the relay will be damaged.
Motor relay 1
Battery connection
Tester connection
Specified condition
-
4 - 5
Open circuit
Connect battery terminal (+) to
terminal No.3
Connect battery terminal (-) to terminal No.1
4 - 5
Continuity (Less than 2 ohms)
Q.
Is the check result normal?
Go to Step 3.
Replace the motor relay 1. Then go to Step 26.
STEP 3. Check the motor relay 2.
caution
Apply battery voltage according to the table below. Never confuse
the positive and negative battery terminals, or the diode inside the relay will be damaged.
Motor relay 2
Battery connection
Tester connection
Specified condition
-
4 - 5
Open circuit
Connect battery terminal (+) to
terminal No.3
Connect battery terminal (-) to terminal No.1
4 - 5
Continuity (Less than 2 ohms)
Q.
Is the check result normal?
Go to Step 4.
Replace the motor relay 2. Then go to Step 26.
STEP 4. Check B-13X motor relay 1 connector, B-12X motor relay 2 connector,
B-107 and B-108 HBB connectors for loose, corroded or damaged terminals, or terminals pushed
back in the connector.
Q.
Is the check result normal?
Go to Step 5.
Repair the faulty connector or terminal. Then go to Step 26.
STEP 5. Check the power supply circuit at B-12X motor relay 2 harness
connector.
(1)Remove the motor relay 2.
(2)Measure the voltage between terminal No.5 and body earth. OK: Approx. 12 volts (battery positive voltage)
Q.
Is battery positive voltage (approx. 12 volts) present?
Go to Step 6.
Go to Step 9.
STEP 6. Check the ignition switch (IG2) circuit at B-12X motor relay
2 harness connector.
(1)Remove the motor relay 2.
(2)Turn the ignition switch to the "ON" position.
(3)Measure the voltage between terminal No.3 and body earth. OK: Approx. 12 volts (battery positive voltage)
Q.
Is battery positive voltage (approx. 12 volts) present?
Go to Step 7.
Go to Step 10.
STEP 7. Check the power supply circuit at B-13X motor relay 1 harness
connector.
(1)Remove the motor relay 1.
(2)Measure the voltage between terminal No.4 and body earth. OK: Approx. 12 volts (battery positive voltage)
Q.
Is battery positive voltage (approx. 12 volts) present?
Go to Step 8.
Go to Step 12.
STEP 8. Check the ignition switch (IG2) circuit at B-13X motor relay
1 harness connector.
(1)Remove the motor relay 1.
(2)Turn the ignition switch to the "ON" position.
(3)Measure the voltage between terminal No.3 and body earth. OK: Approx. 12 volts (battery positive voltage)
Q.
Is battery positive voltage (approx. 12 volts) present?
Go to Step 15.
Go to Step 13.
STEP 9. Check the harness wires between fusible link number 32 and
B-12X motor relay 2 connector terminal No.2.
Q.
Is the check result normal?
Go to Step 26.
Repair or replace it. Then go to Step 26.
STEP 10. Check D-111 intermediate connector, D-230 intermediate connector,
D-34 intermediate connector, D-403 junction block connector and D-405 junction block connector
for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q.
Is the check result normal?
Go to Step 11.
Repair the faulty connector or terminal. Then go to Step 26.
STEP 11. Check the harness wires between B-12X motor relay 2 connector
terminal No.3 and D-403 junction block connector terminal No.2.
Q.
Is the check result normal?
Go to Step 26.
Repair or replace it. Then go to Step 26.
STEP 12. Check the harness wires between fusible link number 32 and
B-13X motor relay 1 connector terminal No.4.
Q.
Is the check result normal?
Go to Step 26.
Repair or replace it. Then go to Step 26.
STEP 13. Check D-231 intermediate connector for loose, corroded or
damaged terminals, or terminals pushed back in the connector.
Q.
Is the check result normal?
Go to Step 14.
Repair or replace it. Then go to Step 26.
STEP 14. Check the harness wires between B-13X motor relay 1 connector
terminal No.3 and multi-purpose fuse number 22 (junction block).
Q.
Is the check result normal?
Go to Step 26.
Repair or replace it. Then go to Step 26.
STEP 15. Check the following harness wires.
The wire between B-108 HBB connector terminal No.31 and
B-12X motor relay 2 connector terminal No.5
The wire between B-107 HBB connector terminal No.2 and B-13X motor relay 1 connector
terminal No.5
Q.
Is the check result normal?
Go to Step 16.
Repair or replace the faulty harness wire. Then go to Step 26.
STEP 16. Check D-256 ABS-ECU connector and D-255 ABS-ECU connector
for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q.
Is the check result normal?
Go to Step 17.
Repair the faulty connector or terminal. Then go to Step 26.
STEP 17. Check the ignition switch (IG2) circuit at D-255 ABS-ECU
harness connector.
(1)Disconnect D-255 ABS-ECU connector.
(2)Turn the ignition switch to the "ON" position.
(3)Measure the voltage between terminal No.38 and body earth. OK: Approx. 12 volts (battery positive voltage)
Q.
Is battery positive voltage (approx. 12 volts) present?
Go to Step 18.
Go to Step 19.
STEP 18. Check the ignition switch (IG2) circuit at D-256 ABS-ECU
harness connector.
(1)Disconnect D-256 ABS-ECU connector.
(2)Turn the ignition switch to the "ON" position.
(3)Measure the voltage between terminal No.6 and body earth. OK: Approx. 12 volts (battery positive voltage)
Q.
Is battery positive voltage (approx. 12 volts) present?
Go to Step 21.
Go to Step 20.
STEP 19. Check the harness wires between D-255 ABS-ECU connector terminal
No.38 and B-12X motor relay 2 connector terminal No.1.
Q.
Is the check result normal?
Go to Step 26.
Repair or replace it. Then go to Step 26.
STEP 20. Check the harness wires between D-256 ABS-ECU connector terminal
No.6 and B-13X motor relay 1 connector terminal No.1.
Q.
Is the check result normal?
Go to Step 26.
Repair or replace it. Then go to Step 26.
STEP 21. Check the HBB.
Check the HBB (continuity and resistance test of the pump motor).
Q.
Is the check result normal?
Go to Step 23.
Go to Step 22.
STEP 22. Check the pump motor and lead wire.
(1)Remove the HBB.
(2)Remove the pump motor and the lead wire from the HBB.
(3)Check the following items:
Confirm that the pump motor operates when the battery voltage is imposed
at the pump motor terminal.
Confirm the continuity of the lead wire.
Q.
Is the check result normal?
Replace the master cylinder and hydraulic unit assembly. Then go to Step 26.
Replace the pump motor or the lead wire. Then go to Step 26.
STEP 23. Check B-107 HBB connector and D-255 ABS-ECU connector for
loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q.
Is the check result normal?
Go to Step 24.
Repair the faulty connector or terminal. Then go to Step 26.
STEP 24. Check the harness wires between D-255 ABS-ECU connector terminal
No.49 and B-107 HBB connector terminal No.4.
Q.
Is the check result normal?
Go to Step 25.
Repair or replace it. Then go to Step 26.
STEP 25. Recheck for diagnosis code.
(1)Erase the diagnosis code.
(2)Recheck for diagnosis code.
Q.
Is code No.53 set?
Replace the ABS-ECU. Then go to Step 26.
It can be assumed that this malfunction is intermittent.
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Go to Step 23.
Go to Step 2.)