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DTC P1238-64: Air decision parts plausibility
 
 
 
 
TECHNICAL DESCRIPTION
Compare the actual measurement of volumetric efficiency by a mass airflow sensor signal with volumetric efficiency estimated from a throttle position sensor (main or sub) signal.
 
 
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)
  • Throttle position sensor
 
 
DTC SET CONDITIONS
Logic Flow Chart
Check Conditions
  • Difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (main) is higher than 0 percent. Or, the volumetric efficiency is 60 percent or lower.
  • Engine speed is 750 r/min or higher.
Judgment Criterion
  • For 4.5 second, the difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (main) is higher than 35 percent.
Check Conditions
  • Difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (sub) is higher than 0 percent. Or, the volumetric efficiency is 60 percent or lower.
  • Engine speed is 750 r/min or higher.
Judgment Criterion
  • For 4.5 second, the difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (sub) is higher than 35 percent.
 
 
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:)
  • Mass airflow sensor system failed.
  • Harness damage in mass airflow sensor system circuit or loose connector contact
  • 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. Using scan tool (M.U.T.-III SE), read the DTC.
Use scan tool (M.U.T.-III SE) to check and see if a DTC other than P1238-64 is set.
Q: Is DTC other than P1238-64 set?
Perform troubleshooting for the set DTC (Refer to DIAGNOSTIC TROUBLE CODE CHART).
 
2.STEP 2. Using scan tool (M.U.T.-III SE), check the data list.
Use scan tool (M.U.T.-III SE) to check the data list (Refer to DATA LIST REFERENCE TABLE).
  • Item number 80: Air flow Sensor
Q: Is the check result normal?
Perform troubleshooting for the mass airflow sensor circuit [Refer to diagnostic trouble code procedure for DTC P0102-00: Air Flow Sensor circuit low input DTC P0102-00: Air Flow Sensor circuit low input), and Refer to diagnostic trouble code procedure for DTC P0103-00: Air Flow Sensor circuit high input DTC P0103-00: Air Flow Sensor circuit high input)].
 
3.STEP 3. 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 P1238-64 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).