Code No. C1860:
Abnormal power supply voltage (too high)
caution
If the EPS-ECU
sets the diagnosis code No. C1860, diagnose the CAN bus lines. If there is any fault in the
CAN bus lines, an incorrect diagnosis code may be set.
Before replacing ECU, ensure that the communication circuit is normal.
DIAGNOSIS CODE SET CONDITIONS
The power supply voltage is more than a predetermined voltage stored in the microcomputer,
and the microcomputer determines that there is a problem in the power supply system.
CRITERIA FOR JUDGING MALFUNCTION
The relay contact voltage is higher than 17.5 V.
PROBABLE CAUSES
Malfunction of the auxiliary battery
Malfunction of the on board charger/on board transformer
Malfunction of the EPS-ECU
DIAGNOSIS PROCEDURE
STEP 1. Check the auxiliary battery voltage.
Start the electric motor unit, and measure the auxiliary battery voltage.
Q.
Does the voltage measure 16 V or less?
Go to Step 2.
Check the auxiliary battery and on board charger/on board transformer,
and repair if necessary. (Refer to GROUP 54A - Auxiliary Battery - Battery
Test as well as GROUP 54D - On Board Charger/On
Board Transformer Removal and Installation .)
STEP 2. Diagnosis code recheck
Recheck if the diagnosis code is set.
(1)Erase the stored diagnosis code.
(2)Turn the electric motor switch to the "LOCK" (OFF) → "ON" position.
(3)Check if the diagnosis code No. C1860 is set.
Q.
Is diagnosis code C1860 set?
Replace EPS-ECU.
Intermittent malfunction. (Refer to GROUP 00 - How to Cope with Intermittent
Malfunction .)
Go to Step 2.
Check the auxiliary battery and on board charger/on board transformer,
and repair if necessary. (Refer to GROUP 54A - Auxiliary Battery - Battery
Test 
as well as GROUP 54D - On Board Charger/On
Board Transformer Removal and Installation 