P1637

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)

Logic Flow Charts (Monitor Sequence):

DTC SET CONDITIONS

Check Conditions
^ Voltage of battery: 9 volts or more.
^ Voltage of battery: 16 volts or less.

Judgement Criteria
^ Calculated checksum is not same as memorized checksum.

OBD-II DRIVE CYCLE PATTERN
All the conditions below continue for 6 seconds.
^ Transmission range switch: D
^ Vehicle speed: 10 km/h (6.2 mph) or more
^ Throttle position: 1/8 or more
^ Engine speed: 450 r/min or more
^ Transmission fluid temperature: 20°C (68°F) or more.
^ Transmission fluid temperature: 99°C (210°F) or more.

PROBABLE CAUSES
^ Damaged wiring harness and connectors
^ Malfunction of TCM (Faulty EEPROM)

DIAGNOSTIC PROCEDURE

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

Q: Is the check result normal?
YES: 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.
NO: Go to Step 2.

STEP 2. Check for open circuit in power supply wiring harness
^ Between relay box and C-40 TCM backup power supply connector (terminal No.31)
^ Between relay box and A-15X CVT control relay (terminal No.4)

Q: Is the check result normal?
YES: Go to Step 3.
NO: Repair the wiring harness.

STEP 3. Symptom recheck after erasing diagnosis code

Q: Is the check result normal?
YES: Intermittent malfunction
NO: Replace TCM.