Code No. P1637: Malfunction of Memory Backup










DIAGNOSTIC FUNCTION


CVT-ECU checks the consistency between EEPROM and the backup memory.

JUDGMENT CRITERIA


When the ignition switch is turned to the ON position, CVT-ECU determines that the writing to the EEPROM area had failed last time the ignition switch was turned to the OFF position.

PROBABLE CAUSES



DIAGNOSTIC PROCEDURE

STEP 1. Check if diagnosis code P1637 is erased by turning the ignition switch from the OFF position to the ON position.

Q. Is the check result normal?
This diagnosis code will be set by disconnecting the battery. If the diagnosis code is not erased by turning the ignition switch to the ON position, it is judged to be normal.
Go to Step 2.

STEP 2. Check for open circuit in power supply wiring harness

  • Between relay box and C-135 CVT-ECU backup power supply connector (terminal No. 31)
  • Between relay box and A-18X CVT control relay (terminal No. 4)

Q. Is the check result normal?
Go to Step 3.
Repair the wiring harness.

STEP 3. Symptom recheck after erasing diagnosis code

Q. Is the check result normal?
Intermittent malfunction
Replace CVT-ECU.