Code No.25: Defective Tyre with Different Diameter
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If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Diagnose the CAN bus lines before the diagnosis codes (Refer to GROUP 54D, CAN bus-line diagnostic flow  ).
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OPERATION
- A toothed rotor generates a voltage signal as it moves across the pickup field of each wheel speed sensor.
- The amount of voltage generated at each wheel is determined by the clearance between the rotor teeth and the wheel speed sensor, and by the speed of rotation.
- The wheel speed sensors transmit the frequency of the voltage signal to the Active stability and traction control system-electronic control unit (ASTC-ECU).
- The ABS hydraulic unit modulates the amount of braking force individually applied to each wheel cylinder.
DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set when diagnosis codes No. 11, 12, 13, 14, 21, 22, 23, and 24 are not set, the lowest wheel speed is 30 km/h or more, and the output signal from any of the wheel speed sensors is more than 1.2 times as large as that from the wheel speed sensor of the lowest speed wheel.
PROBABLE CAUSES
The most likely causes for these diagnosis codes to set are:
- Too high or low tyre pressure
- Varying tyre size
- Tyres with different brands and different types
- Tyres with different degrees of wear
- Flat tyre
- Malfunction of the ASTC-ECU
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STEP 1. M.U.T.-III CAN bus diagnostics
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Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
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(1)Connect M.U.T.-III to the 16-pin diagnosis connector.
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(2)Turn the ignition switch to the "ON" position.
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(3)Diagnose the CAN bus line.
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(4)Turn the ignition switch to the "LOCK" (OFF) position.
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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 line (Refer to GROUP 54D, CAN bus line Diagnostic flow ). Then go to Step 2.
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STEP 2. Check whether the diagnosis code is reset.
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Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.
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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)Disconnect the M.U.T.-III.
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(6)Drive the vehicle more than 60 seconds at the speed exceeds to 30 km/h to judge the wheel speed signal to the ASTC-ECU.
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(7)Check if the diagnosis code is set.
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(8)Turn the ignition switch to the "LOCK" (OFF) position.
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Go to Step 3.
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The procedure is complete.
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STEP 3. Check the tyre size.
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Check if the tyres of 4 wheels installed at present are uniform and adequate in size, brand, and type.
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Q.
Is the check result normal?
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Go to Step 4.
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Use 4 wheels with the same and adequate tyre size. Then go to Step 6.
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STEP 4. Check the tyre pressure.
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Check if each tyre pressure of the 4 wheels installed at present is adequate.
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Q.
Is the check result normal?
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Go to Step 5.
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Adjust the pressure to be adequate. Then go to Step 6.
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STEP 5. Check whether the diagnosis code is reset.
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Check again if the diagnosis code is set.
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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)Disconnect the M.U.T.-III.
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(6)Drive the vehicle more than 60 seconds at the speed exceeds to 30 km/h to judge the wheel speed signal to the ASTC-ECU.
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(7)Check if the diagnosis code is reset.
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(8)Turn the ignition switch to the "LOCK" (OFF) position.
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Replace the ASTC-ECU. Then go to Step 6.
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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 6. Check whether the diagnosis code is reset.
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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)Disconnect the M.U.T.-III.
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(6)Drive the vehicle more than 60 seconds at the speed exceeds to 30 km/h to judge the wheel speed signal to the ASTC-ECU.
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(7)Check if the diagnosis code is set.
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(8)Turn the ignition switch to the "LOCK" (OFF) position.
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Repeat the troubleshooting from Step 1.
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The procedure is complete.
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