P1238

DTC P1238: Mass Airflow Sensor Plausibility (Torque Monitor)

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 stored in memory for the item monitored below)
- Not applicable

Sensor (The sensor below is determined to be normal)
- Not applicable

DTC SET CONDITIONS

DTC Set Conditions:

Check Conditions
- Engine speed is 750 r/min or higher.
- Except while fuel is being shut off.

Judgment Criterion
- For 0.9 second, the difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (main) is 45 percent or more.

or

- For 0.9 second, the difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (sub) is 45 percent or more.

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 16. OBD- II Drive Cycle

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Mass airflow sensor system failed.
- ECM failed.

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A

STEP 1. Using scan tool MB991958, read the diagnostic trouble code (DTC).







CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Read the DTC.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the diagnostic trouble code other than P1238 set?

YES : Refer to, Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions

NO : Go to Step 2.

STEP 2. Using scan tool MB991958, check data list item 10: Mass Airflow Sensor.

1. Start the engine and run at idle.
2. Set scan tool MB991958 to the data reading mode for item 10, Mass Airflow Sensor.
3. Warm up the engine to normal operating temperature: 80°C to 95°C (176°F to 203°F).
- The standard value during idling should be between 1,350 and 1,670 millivolts.
- When the engine is revved, the mass airflow rate should increase according to the increase in engine speed.

4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the sensor operating properly?

YES : Go to Step 3.

NO : Refer to, DTC P0101 -Mass Airflow Circuit Range/Performance Problem P0101, DTC P0102 -Mass Airflow Circuit Low Input P0102, DTC P0103 -Mass Airflow Circuit High Input P0103.

STEP 3. Check the trouble symptoms.

1. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 16. OBD- II Drive Cycle
2. Check the diagnostic trouble code (DTC).

Q: Is DTC P1238 set?

YES : Replace the ECM. When the ECM is replaced, register the ID code. Then go to Step 4.

NO : It can be assumed that this malfunction is intermittent.

STEP 4. Test the OBD-II drive cycle.

1. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 16. OBD- II Drive Cycle
2. Check the diagnostic trouble code (DTC).

Q: Is DTC P1238 set?

YES : Retry the troubleshooting.

NO : The inspection is complete.