Procedures

TIMING CHAIN MAINTENANCE

If the vehicle equipped with 4B11-T/C engine continues the rough driving like competitive running*�, the amount of carbon mixed into the engine oil tends to increase. This can possibly cause the timing chain to gradually elongate. To prevent this, the function or logic monitoring the amount of elongation of the timing chain is integrated into the ECM. When the ECM detects the elongation of the timing chain, the warning is shown on the multi-information display of combination meter as shown in the illustration. This gives the driver the information that the visual check of the elongation of the timing chain is necessary. If this warning is continuously neglected, the timing chain can possibly interfere with the other engine components, resulting in the engine damaged.

NOTE: *1:
The competitive running means the running that constantly repeats the cycle of the full opened position of the accelerator pedal and the full closed position of the accelerator pedal.

The ECM stores the timing chain conditions as the learning value when the timing chain is installed. The ECM stores the amount of elongation of the timing chain in the EEPROM as the current learning value, compared with the learning value. The ECM judges that the visual check of the elongation of the timing chain is necessary when the current learning value exceeds the specified value. Thus, use the scan tool MB991958 to always carry out the maintenance of the learning value related to the timing chain that is stored by the ECM after the following service.

LEARNED VALUE READ & SAVE AND WRITE

LEARNED VALUE (CHANGED ECU)

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

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. After the ignition switch is in "LOCK" (OFF) position, connect scan tool MB991958 to the diagnosis connector.
2. Turn the ignition switch to the "ON" position.
3. Select "MFI" from System select Screen of scan tool MB991958.
4. Select "Special Function" from MFI Screen.
5. Select "Timing chain maintenance" from Special Function Screen.
6. Select "Learned value Read&Save" from Timing chain maintenance Screen.
7. Press "OK" to store the learning value file.

NOTE:
When the learning value file is appropriately stored, "Learned value Save Complete" is shown on the screen of the scan tool MB991958.

NOTE:
Calculating the amount of elongation of the timing chain by the ECM takes the time. Thus, the file cannot be stored fora while after the ECM initialization or replacement.

8. Replace the ECM.
9. Select "Learned value reset" from Timing chain maintenance Screen.
10. Select the learning value file stored during Step 3 to write the learning value.

NOTE:
Use only the learning value file stored during Step 3 without using any other files.

NOTE:
When the learning value is appropriately written, "Learned value writing Completed." is shown on the screen of the scan tool MB991958.

LEARNED VALUE RESET

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

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.