Code No.C1278:
Solenoid valve relay (open circuit)
Code No.C1279: Solenoid valve relay (short circuit)
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- If there is any
problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis,
diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table
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- Whenever ECU is replaced, ensure that the CAN bus lines are normal.
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OPERATION
The ABS-ECU contains the power supply circuit (+BV terminal) for the solenoid
valve. The solenoid valve is energised by the valve relay, which is incorporated in the ABS-ECU.
DIAGNOSIS CODE SET CONDITIONS
These diagnosis codes will be set under the cases below.
Code No. C1278
- When the solenoid valve relay monitor judges that the solenoid valve relay is turned
"OFF" although it actually is turned "ON"
Code No. C1279
- When the solenoid valve relay monitor judges that the solenoid valve relay is turned
"ON" although it actually is turned "OFF"
PROBABLE CAUSES
The most likely causes for these diagnosis codes to set are:
- Battery failure
- Fusible link malfunction
- Damaged wiring harness or connector
- Malfunction of the hydraulic unit assembly (integrated with ABS-ECU)
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STEP 1. M.U.T.-III CAN bus diagnosis
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Use M.U.T.-III to diagnose the CAN bus lines.
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Q.
Is the check result normal?
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 Go to Step 3.
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 Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
On completion, go to Step 2.
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STEP 2. Diagnosis code recheck after resetting CAN bus lines
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(1)Turn the ignition switch to the "ON" position.
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(2)Erase the diagnosis code.
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(3)Turn the ignition switch to the "LOCK" (OFF) position.
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(4)Turn the ignition switch to the "ON" position.
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(5)Check if the diagnosis code is set.
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(6)Turn the ignition switch to the "LOCK" (OFF) position.
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Q.
Is code No.C1278 or C1279 set?
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Go to Step 3.
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Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent
Malfunctions ).
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STEP 3. Check the battery.
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Refer to GROUP 54A - Battery Test .
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Q.
Is the auxiliary battery normal?
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Go to Step 4.
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Charge or replace the battery. Then go to Step 9.
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STEP 4. Check the fusible link No.SBF2
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Q.
Is the check result normal?
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Go to Step 6.
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Go to Step 5.
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STEP 5. Measure the resistance at the ABS-ECU connector
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(1)Remove the fusible link No.SBF2.
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(2)Check the ABS-ECU connector.
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(3)Disconnect the connector and measure at the wiring harness side.
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(4)Measure the resistance between +BV terminal and body earth.
OK: No continuity
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Q.
Is the check result normal?
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Replace the fusible link No.SBF2. Then go to Step 9.
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The power supply circuit may be short. Repair the wiring harness wires or connectors
between the ABS-ECU connector +BV terminal and the fusible links, or replace the fusible
links. Then go to Step 9.
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STEP 6. Measure the voltage at the ABS-ECU connector
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(1)Check the ABS-ECU connector.
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(2)Disconnect the connector and measure at the wiring harness side.
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(3)Measure the voltage between +BV terminal and body earth.
OK: Battery voltage
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Q.
Is the check result normal?
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Go to Step 7.
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The power supply circuit may be open. Repair the wiring harness wires or connectors
between the ABS-ECU connector +BV terminal and the fusible links. Then go to Step 9
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STEP 7. Measure the resistance at the ABS-ECU connector
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(1)Disconnect the connector and measure at the wiring harness side.
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(2)Measure the resistance between terminals GND1 or GND2 and body earth.
OK: Continuity exists (2 Ω or less).
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Q.
Is the check result normal?
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Go to Step 8.
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An open circuit may be present in the earth circuit. Repair the wiring harness
wires between ABS-ECU connector terminal GND1 or GND2 and body earth. Then go to Step 9.
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STEP 8. Check whether the diagnosis code is set again.
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(1)Turn the ignition switch to the "ON" position.
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(2)Erase the diagnosis code.
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(3)Turn the ignition switch to the "LOCK" (OFF) position.
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(4)Turn the ignition switch to the "ON" position.
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(5)Check that the ABS warning lamp and brake warning lamp goes out.
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(6)Check if the diagnosis code is set.
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(7)Turn the ignition switch to the "LOCK" (OFF) position.
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Q.
Is diagnosis code No. C1278 or C1279 set?
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Replace the hydraulic unit assembly (integrated with ABS-ECU) (Refer to ).
Then go to Step 9.
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Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent
Malfunctions ).
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STEP 9. Check whether the diagnosis code is set again.
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(1)Turn the ignition switch to the "ON" position.
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(2)Erase the diagnosis code.
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(3)Turn the ignition switch to the "LOCK" (OFF) position.
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(4)Turn the ignition switch to the "ON" position.
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(5)Check that the ABS warning lamp and brake warning lamp goes out.
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(6)Check if the diagnosis code is set.
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(7)Turn the ignition switch to the "LOCK" (OFF) position.
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Q.
Is diagnosis code No. C1278 or C1279 set?
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Return to Step 1.
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This diagnosis is complete.
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