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DTC P0638-00: Throttle Valve Control Servo Circuit Range/Performance Problem
 
 
 
 
CIRCUIT OPERATION
  • The throttle actuator is built into the throttle body assembly.
  • The ECM controls the current that is applied from the ECM connector terminal number 17 and number 18 to the throttle actuator terminal number 1 and number 2 of the throttle valve assembly connector.
 
 
TECHNICAL DESCRIPTION
ECM checks the electronic controlled throttle system for abnormal conditions.
 
 
DESCRIPTIONS OF MONITOR METHODS
Difference between throttle position sensor (main) output and target opening is greater than the specified value.
 
 
MONITOR EXECUTION
Continuous.
 
 
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC set in memory for the item monitored below)
  • Not applicable
Sensor (The sensor below is determined to be normal)
  • Not applicable
 
 
DTC SET CONDITIONS
Check Conditions
  • 12V battery positive voltage is higher than 8.3 volts.
  • Throttle position sensor (main) output voltage is between 0.2 and 4.8 volts.
  • Drop of throttle position sensor (main) output voltage per 100 milliseconds is higher than 0.04 volt.
Judgment Criterion
  • The target throttle position sensor (main) voltage subtracted from the throttle position sensor (main) output voltage is higher than 0.5 volt for 0.4 second.
Check Conditions
  • 12V battery positive voltage is higher than 8.3 volts.
  • Throttle position sensor (main) output voltage is between 0.2 and 4.8 volts.
  • Target throttle position sensor (main) voltage is lower than 1.5 volts.
Judgment Criterion
  • Difference between throttle position sensor (main) output voltage and target throttle position sensor (main) voltage is 0.6 volt or higher for 0.4 second.
Check Conditions
  • 12V battery positive voltage is higher than 8.3 volts.
  • Throttle position sensor (main) output voltage is between 0.2 and 4.8 volts.
Judgment Criterion
  • Difference between throttle position sensor (main) output voltage and target throttle position sensor (main) voltage is 1 volt or higher for 0.4 second.
Check Condition
  • 12V starter battery positive voltage is higher than 8.3 volts.
Judgment Criterion
  • Throttle position sensor (main) default opening learnt value is 4 volts or higher.
 
 
FAIL-SAFE AND BACKUP FUNCTION
Throttle opening degree position is in default position.
 
 
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function, OBD-II Drive Cycle – Pattern 1 OBD- II DRIVE CYCLE.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • Throttle actuator (built into the throttle body assembly) failed (throttle valve operation).
  • Throttle actuator circuit harness damage or connector damage.
  • ECM failed.
 
 
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
1.STEP 1. Check throttle body.
Throttle actuator check (Refer to THROTTLE ACTUATOR CONTROL MOTOR CHECK).
Q: Is the check result normal?
Repair throttle body assembly (throttle actuator) (Refer to THROTTLE BODY ASSEMBLY ).
 
2.STEP 2. Check harness between throttle body assembly connector terminal number 1 and ECM connector terminal number 17.
Check signal line for damage.
Q: Is the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
3.STEP 3. Check harness between throttle body assembly connector terminal number 2 and ECM connector terminal number 18.
Check output line for damage.
Q: Is the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
4.STEP 4. Test the OBD-II drive cycle.
After erasing the DTC, carry out test drive with the drive cycle pattern, and recheck the DTC.
(1) Use scan tool (M.U.T.-III SE) to erase the DTC.
(2) Carry out test drive with the drive cycle pattern (Refer to Diagnostic Function, OBD-II Drive Cycle – Pattern 1 OBD- II DRIVE CYCLE).
(3) Use scan tool (M.U.T.-III SE) to recheck the DTC.
Q: Is DTC P0638-00 set?
Replace the ECM (Refer to ENGINE CONTROL MODULE (ECM) REMOVAL AND INSTALLATION).
Intermittent malfunction (Refer to GENERAL INFORMATION, General Information – How to Use Troubleshooting/Inspection Service Points – How to Cope with Intermittent Malfunctions HOW TO COPE WITH INTERMITTENT MALFUNCTIONS).