Code No.54: Motor relay system (open circuit, short circuit or motor relay
coil defect)
OPERATION
- The motor relay 1 and the motor relay 2 are controlled by the
ASTC-ECU.
- If the brake fluid pressure in the hydraulic brake booster (HBB) becomes
low, the ASTC-ECU outputs the motor relay actuating signal to the motor
relay 1 and the motor relay 2 and then the pump motor operates.
- The ASTC-ECU monitors the pump motor (at 25 terminal).
DIAGNOSIS CODE SET CONDITIONS
Diagnosis code No.54 is set if the
motor relay circuit is open or short, the motor relay 1 or the motor relay 2
is defective, or the internal circuit of the ASTC-ECU is defective.
PROBABLE CAUSES
- Malfunction of the motor relay 1 or the motor relay 2
- Damaged wiring harness or connector
- Malfunction of the ASTC-ECU
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STEP 1. M.U.T.-III diagnosis code.
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(1)Erase the diagnosis code.
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(2)Recheck for diagnosis code.
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 Carry out the troubleshooting
for code No.55 (Refer to  ). Then go to Step 27.
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 Go to Step 2.
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STEP 2. Check the pump motor operation.
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(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.
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(2)Turn the ignition switch to the "ON" position.
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Q.
Does the pump motor operate?
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Go to Step 24.
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Go to Step 3.
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STEP 3. Check the motor relay 1.
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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.
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BATTERY
CONNECTION
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TESTER
CONNECTION
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SPECIFIED
CONDITION
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4 - 5
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Open circuit
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- Connect battery terminal (+) to terminal 3
- Connect battery terminal (-) to terminal 1
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4 - 5
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Continuity (Less than 2
ohms)
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Replace the relay. Then go to
Step 27.
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Go to Step 4.
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STEP 4. Check the motor relay 2.
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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.
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BATTERY
CONNECTION
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TESTER
CONNECTION
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SPECIFIED
CONDITION
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-
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4 - 5
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Open circuit
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- Connect battery terminal (+) to terminal 3
- Connect battery terminal (-) to terminal 1
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4 - 5
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Continuity (Less than 2
ohms)
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Replace the relay. Then go to
Step 27.
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Go to Step 5.
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STEP 5. Check motor relay 1 connector B-13X, motor relay 2 connector
B-12X, HBB connectors B-107 and B-108 for loose, corroded or damaged
terminals, or terminals pushed back in the connector.
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Q.
Is the check result normal?
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Go to Step 6.
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Repair the faulty connector or
terminal. Then go to Step 27.
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STEP 6. Check the power supply circuit at motor relay 2 harness
connector B-12X.
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(1)Remove the motor relay 2.
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(2)Measure the voltage between terminal 5 and body
earth.
OK: Approx. 12 volts (battery positive
voltage)
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Q.
Is battery positive voltage (approx. 12 volts) present?
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Go to Step 7.
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Go to Step 10.
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STEP 7. Check the ignition switch (IG2) circuit at motor relay 2
harness connector B-12X.
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(1)Remove the motor relay 2.
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(2)Turn the ignition switch to the "ON" position.
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(3)Measure the voltage between terminal 3 and body
earth.
OK: Approx. 12 volts (battery positive
voltage)
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Q.
Is battery positive voltage (approx. 12 volts) present?
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Go to Step 8.
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Go to Step 11.
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STEP 8. Check the power supply circuit at motor relay 1 harness
connector B-13X.
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(1)Remove the motor relay 1.
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(2)Measure the voltage between terminal 4 and body
earth.
OK: Approx. 12 volts (battery positive
voltage)
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Q.
Is battery positive voltage (approx. 12 volts) present?
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Go to Step 9.
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Go to Step 13.
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STEP 9. Check the ignition switch (IG2) circuit at motor relay 1
harness connector B-13X.
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(1)Remove the motor relay 1.
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(2)Turn the ignition switch to the "ON" position.
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(3)Measure the voltage between terminal 3 and body
earth.
OK: Approx. 12 volts (battery positive
voltage)
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Q.
Is battery positive voltage (approx. 12 volts) present?
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Go to Step 16.
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Go to Step 14.
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STEP 10. Check the harness wires between fusible link number 32 and
motor relay 2 connector B-12X (terminal 5).
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Q.
Is the check result normal?
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Go to Step 27.
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Repair or replace it. Then go to
Step 27.
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STEP 11. Check intermediate connectors D-113 <4M4>, D-111
<6G7>, D-34 junction block connector D-403 and junction block
connector D-405 for loose, corroded or damaged terminals, or terminals
pushed back in the connector.
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Q.
Is the check result normal?
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Go to Step 12.
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Repair or replace it. Then go to
Step 27.
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STEP 12. Check the harness wires between motor relay 2 connector B-12X
(terminal 3) and junction block connector D-403 (terminal
2).
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Q.
Is the check result normal?
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Go to Step 27.
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Repair or replace it. Then go to
Step 27.
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STEP 13. Check the harness wires between fusible link number 32 and
motor relay 1 connector B-13X (terminal 4).
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Q.
Is the check result normal?
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Go to Step 27.
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Repair or replace it. Then go to
Step 27.
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STEP 14. Check intermediate connector D-231 for loose, corroded or
damaged terminals, or terminals pushed back in the
connector.
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Q.
Is the check result normal?
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Go to Step 15.
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Repair or replace it. Then go to
Step 27.
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STEP 15. Check the harness wires between motor relay 1 connector B-13X
(terminal 3) and multi-purpose fuse number 22 (junction
block).
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Q.
Is the check result normal?
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Go to Step 27.
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Repair or replace it. Then go to
Step 27.
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STEP 16. Check the following harness wires.
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- The wire between HBB connector B-108 (terminal 31) and motor relay 2
connector B-12X (terminal 4)
- The wire between HBB connector B-107 (terminal 2) and motor relay 1
connector B-13X (terminal 5)
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Q.
Is the check result normal?
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Go to Step 17.
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Repair or replace the faulty
harness wire. Then go to Step 27.
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STEP 17. Check ASTC-ECU connector D-233 and D-232 for loose, corroded
or damaged terminals, or terminals pushed back in the
connector.
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Q.
Is the check result normal?
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Go to Step 18.
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Repair the faulty connector or
terminal. Then go to Step 27.
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STEP 18. Check the ignition switch (IG2) circuit at ASTC-ECU harness
connector D-232.
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(1)Disconnect ASTC-ECU connector D-232.
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(2)Turn the ignition switch to the "ON" position.
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(3)Measure the voltage between terminal 48 and body
earth.
OK: Approx. 12 volts (battery positive
voltage)
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Q.
Is battery positive voltage (approx. 12 volts) present?
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Go to Step 19.
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Go to Step 20.
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STEP 19. Check the ignition switch (IG2) circuit at ASTC-ECU harness
connector D-233.
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(1)Disconnect ASTC-ECU connector D-233.
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(2)Turn the ignition switch to the "ON" position.
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(3)Measure the voltage between terminal 24 and body
earth.
OK: Approx. 12 volts (battery positive
voltage)
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Q.
Is battery positive voltage (approx. 12 volts) present?
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Go to Step 22.
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Go to Step 21.
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STEP 20. Check the harness wires between ASTC-ECU connector D-232
(terminal 48) and motor relay 2 connector B-12X (terminal
1).
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Q.
Is the check result normal?
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Go to Step 27.
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Repair or replace it. Then go to
Step 27.
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STEP 21. Check the harness wires between ASTC-ECU connector D-233
(terminal 24) and motor relay 1 connector B-13X (terminal
1).
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Q.
Is the check result normal?
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Go to Step 27.
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Repair or replace it. Then go to
Step 27.
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STEP 22. Check the HBB (continuity and resistance test of the pump
motor).
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(1)Disconnect HBB connectors B-107 and B-108.
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(2)Check for continuity and measure the resistance between
terminals at the HBB connectors.
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TESTER
CONNECTION
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SPECIFIED
CONDITION
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RESISTANCE Ω
(REFERENCE VALUE)
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2 - 7
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Continuity
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10 or less
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2 - 31
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Continuity
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Less than 2
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4 - 32
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Continuity
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Approx. 33
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7 - 32
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Continuity
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Less than 2
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31 - 32
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Continuity
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10 or less
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Q.
Does continuity exist between above terminals?
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Go to Step 24.
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Go to Step 23.
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STEP 23. Check the pump motor and lead wire.
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(1)Remove the HBB (Refer to ).
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(2)Remove the pump motor and the lead wire from the HBB
(Refer to ).
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(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.
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Q.
Are both of the pump motor and the lead wire in good condition?
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Replace the master cylinder and
hydraulic unit assembly (Refer to ). Then go to Step 27.
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Replace the pump motor or the
lead wire (Refer to ). Then go to Step 27.
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STEP 24. Check HBB connector B-107 and ASTC-ECU connector D-233 for
loose, corroded or damaged terminals, or terminals pushed back in the
connector.
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Q.
Is the check result normal?
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Go to Step 25.
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Repair the faulty connector or
terminal. Then go to Step 27.
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STEP 25. Check the harness wires between ASTC-ECU connector D-233
(terminal 25) and HBB connector B-107 (terminal 4).
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Q.
Is the check result normal?
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Go to Step 26.
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Repair or replace it. Then go to
Step 27.
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STEP 26. Recheck for diagnosis code.
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(1)Erase the diagnosis code.
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(2)Recheck for diagnosis code.
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Replace the ASTC-ECU (Refer to
GROUP 35C, ASTC-ECU ). Then go to Step 27.
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It can
be assumed that this malfunction is intermittent. Refer to GROUP 00, How to
Use Troubleshooting/Inspection Service Points - How to Cope
with Intermittent Malfunction .
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STEP 27. Recheck for diagnosis code.
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(1)Erase the diagnosis code.
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(2)Recheck for diagnosis code.
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Start over at Step 1.
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The
procedure is complete.
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