A/T Controls - Harsh Reverse Engagement During Warm Up
37 Harsh reverse gear engagement during engine warm-up37 10 10
2020452/3
June 29, 2010
Supersedes Technical Service Bulletin Group 37 number 09-04 dated April 17, 2009 for reasons listed below.
Affected Vehicles
Condition
Harsh engagement of reverse gear R during the warm-up phase. This condition may occur up to an ATF temperature of 60°C. The concern may occur when maneuvering the vehicle in parking lots. If the vehicle is moved to D after reversing, there can be a harsh gear engagement when reverse gear R is engaged again.
Technical Background
When reverse gear R is engaged, the reverse clutch is filled with ATF. The reverse clutch empties itself when the vehicle then drives forward, depending on time and the speed of the vehicle. The TCM adaptation of the reverse clutch does not measure the fill time of the reverse clutch in the temperature range of 10-60°C. If the reverse clutch has emptied in this temperature range, a harsh engagement may be noticed when reverse gear R is engaged.
Production Solution
New software for the Transmission Control Module (J217) addresses the condition.
Service
Try to reproduce the customer complaint so that it can be clearly assigned to this TSB.
If the condition is verified, update the transmission control module per the software table below.
Tip: If the adaptation is not possible in Guided Fault Finding due to a missing engine speed error, instructions for adapting the 0AW clutches with self-diagnosis are below.
SVM Update Instructions
1. Follow all instructions in the attached TSB 2011732 00 Software Version Management (SVM), operating instructions.
2. Update the Transmission Control Unit (J217) using the SVM action code as listed in the table above if necessary.
3. After the SVM update, the programmed values of the clutches must be reset as follows:
a. In Guided Functions, select Transmission Electronics >> Adjustment.
After starting this function, the following question appears: "Have you replaced the control unit for the automatic gearbox?"
b. Answer Yes.
Now the entry can be deleted and the adaptation of the clutches carried out.
4. Attempt the GFF clutch adaptation test plan. If the test plans fails to adapt the clutches, perform the 0AW Self-Diagnosis Clutch Adaptation Instructions below.
0AW Self-Diagnosis Clutch Adaptation Instructions
Select the following measured values in the self-diagnosis and possibly save them under Favorites:
^ Adaptation of the forwards start-up behavior [LO] State
^ Adaptation of the backwards start-up behavior [LO] State
^ Transmission fluid temperature
^ Specified clutch torque
Creep adaptation of the forward and reverse clutch with 0AW gearboxes:
1. Make sure that there are no fault entries in the TCM.
2. Warm up the gearbox to about 85°C, ideally by pulling away in driving mode D and R at various loads of max. 1500 rpm.
Tip: Currently the adaptation is only possible when the measured value transmission temperature is between 80° - 95°C.
3. When the vehicle is standing still, select driving mode D.
4. Pull away with little acceleration to about 6 mph or 10 km/h. Slowly brake the vehicle with the foot brake. Hold the brake pedal for another 5-10 seconds as the vehicle stands still.
5. When stopping, the specified clutch torque must not drop below 20 Nm, otherwise the adaptation fails. If this is the case, change the driving profile (less load, gentler braking).
6. Repeat step 4 until the measured value indicates the adaptation of the forwards start-up behavior is successfully completed.
7. With the vehicle standing still, select driving mode R.
8. Repeat step 4 until the measured value indicates adaptation of the backwards start-up behavior is successfully completed.
When stopping, the specified clutch torque must not drop below 20 Nm, otherwise the adaptation fails.
If this is the case, change the driving profile.
9. After a terminal 15 reset, the adaptation starts over again with status running. Keep the ignition switched on for at least six minutes after a successful adaptation.
Tip: The ignition must not be switched off during this time period.
Warranty
Additional Information
The following Technical Service Bulletin will be necessary to complete this procedure:
^ TSB 2011732 00 Software Version Management (SVM), operating instructions.
All part and service references provided in this TSB are subject to change and/or removal. Always check with your Parts Dept. and service manuals for the latest information.
Attachment - TSB 2011732 00 Software Version Management (SVM), operating instructions.