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DTC P1637: Malfunction of Memory Backup
 
 

 
 
 
 
DIAGNOSTIC FUNCTION
TCM checks the consistency between EEPROM and the backup memory.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • When the ignition switch is turned to the "ON" position, TCM determines that the writing to the EEPROM area had failed last time the ignition switch was turned to the "LOCK" (OFF) position.
 
 
MONITOR EXECUTION
  • Continuous
 
 
MONITOR EXECUTION CONDITIONS (OTHER MONITOR AND SENSOR)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
  • Not applicable
Sensor (The sensor below is determined to be normal)
  • Not applicable
 
 
LOGIC FLOW CHARTS (Monitor Sequence)
 
 
DTC SET CONDITIONS
Judgment Criteria
  • Calculated checksum is not same as memorized checksum.
 
 
OBD-II DRIVE CYCLE PATTERN
Ignition switch: ON (start the engine and keep it for 10 seconds or more)
 
 
PROBABLE CAUSES
  • Damaged wiring harness and connectors
  • Malfunction of TCM (Faulty EEPROM)
 
 
DIAGNOSIS
STEP 1. Check if diagnostic trouble code P1637 is erased by turning the ignition switch from the "LOCK" (OFF) position to the "ON" position.
Is the check result normal?
This diagnostic trouble code will be set by disconnecting the battery. If the diagnostic trouble code is 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-130 TCM backup power supply connector (terminal No.31)
  • Between relay box and A-69X CVT control relay (terminal No.4)
Is the check result normal?
Go to Step 3.
Repair the wiring harness.
 
STEP 3. Symptom recheck after erasing diagnostic trouble code
Is the check result normal?
Intermittent malfunction
Replace TCM.