Code No. P1B26:
Different diameter tyres on front and rear wheels (when learning is completed) Code
No. P1B27: Different diameter tyres on front and rear wheels (when learning is not completed)
caution
If there is any problem in the CAN bus lines,
an incorrect diagnosis code may be set. Prior to this diagnosis, always diagnose the CAN bus
lines.
OPERATION
ASC-ECU communicates with EV-ECU via CAN.
DIAGNOSIS CODE SET CONDITIONS
If the tyre radius ratio learned value is specified value
or more during the EV-ECU control power supply relay ON, the diagnosis code No. P1B26 will be
set.
During the traction control, if the TLC calculation torque specified value is lower,
the diagnosis code No. P1B27 will be set.
PROBABLE CAUSES
The wheel is equipped with a different diameter tyre.
Improper tyre pressure
Malfunction of ASC-ECU
Malfunction of the EV-ECU
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnosis
Use the M.U.T.-III to diagnose the CAN bus lines.
Q.
Is the check result normal?
Go to Step 3.
Repair the CAN bus line. (Refer to GROUP 54C - Troubleshooting .)
Then go to Step 2.
STEP 2. Diagnosis code recheck after resetting CAN bus lines
Check again if the diagnosis code No. P1B26 or No. P1B27 is set to the EV-ECU.
(1)Erase the stored diagnosis code.
(2)Set the electric motor switch from the "LOCK" (OFF) position to the "ON" position.
(3)Drive the vehicle at 10 km/h or more, 10 seconds or more.
(4)Check if the diagnosis code is set.
Q.
Is the diagnosis code set?
Go to Step 3.
This diagnosis is complete.
STEP 3. Check the tyre pressure.
Check the tyre pressure. (Refer to GROUP 31 - On-vehicle Service .)
Q.
Is the check result normal?
Go to Step 4.
Check the tyre and adjust the tyre pressure.
STEP 4. Tyre check
Check the tyre size, difference of right and left, brand, wear difference, etc.
Q.
Is the check result normal?
Go to Step 5.
Replace the tyre.
STEP 5. Use M.U.T.-III to confirm a diagnosis code of other systems.
Check if diagnosis code is set to the ASC-ECU.
Q.
Is the diagnosis code set?
Perform troubleshooting for ASC. (Refer to GROUP 35C - Diagnosis Code
Chart .) Then go to Step 6.
Replace the EV-ECU. (Refer to .) Then go to
Step 6.
STEP 6. Diagnosis code recheck
Check again if the diagnosis code is set to the EV-ECU.
(1)Erase the stored diagnosis code.
(2)Set the electric motor switch from the "LOCK" (OFF) position to the "ON" position.
(3)Drive the vehicle at 10 km/h or more, 10 seconds or more.
Go to Step 3.
Repair the CAN bus line. (Refer to GROUP 54C - Troubleshooting 
.)
Then go to Step 2.