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DTC P1637: Malfunction of Memory Backup
 
 
 
 
DIAGNOSTIC FUNCTION
The TCM determines that the system is defective if the calculated value does not correspond with the stored value.
 
 
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
Check Condition
  • Ignition switch is "ON" position
Judgment Criteria
  • Calculated checksum is not same as memorized checksum.
 
 
OBD-II DRIVE CYCLE PATTERN
Ignition switch: "ON" position (start the engine and keep it for 10 seconds or more)
 
 
PROBABLE CAUSES
Malfunction of TCM
 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: Vehicles Communication Interface (V.C.I.)
    • MB991827: M.U.T.-III USB Cable
    • MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
STEP 1. Using scan tool (M.U.T.-III), check the other DTC(s) is stored.
Check if DTC(s) other than DTC P1637 is stored.
Is the DTC stored?
Carry out the appropriate troubleshooting (Refer to ).
Go to Step 2.
 
STEP 2. Using scan tool (M.U.T.-III), recheck the DTC.
Check again if the DTC is stored.
(1) Erase the DTC.
(2) Turn the ignition switch to the "LOCK" (OFF) position.
(3) Carry out a test drive with the OBD-II drive cycle pattern.
(4) Recheck the DTC.
Is DTC P1637 stored?
Replace the TCM (Refer to ).
The trouble can be an intermittent malfunction (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).