A/T - ECO Start/Stop Inoperative, DTC P0944 Stored In TCM

Mercedes Benz C 250 (204.052) (CANADA) V6-2.5L (272.921) Technical Service Bulletin # LI27-57_P-0534962 Date: 120522

A/T - ECO Start/Stop Inoperative, DTC P0944 Stored In TCM

ECO start/stop inoperative, fault code P0944 in transmission control unit

Topic number LI27.57-P-053496

Version 2

Design group 27.57 Oil pump

Date 05-22-2012

Validity NAG2 FEPlus (722.9) with auxiliary oil pump with code B03 up to transmission sequence number 7.248.200

Reason for change Model series 251 deleted because model series 251 does not have ECO start/stop.

Complaint:

ECO start/stop inoperative, fault code P0944 in transmission control unit.

Attachments

Cause:

Check valve in torque converter housing may be damaged. Leakage between torque converter housing and auxiliary oil pump.

May affect transmissions with transmission sequence numbers starting with -07-xxx xxx.

Remedy:

Access via fault code P0944; and perform there the following test according to the instructions:

Page 15

Check the check valve in the torque converter housing (in pressure duct) for damage (see pictures in attachment).

If the check valve is damaged, the torque converter housing and the auxiliary oil pump (component M42) must be re-placed. When

removing/installing the automatic transmission auxiliary oil pump, observe AR 27.30-P-0651EL.

Important note:

After the test/repair, check and correct the oil level in the transmission.

If no damage is found on the check valve, but a torque converter housing with object number 212 271 0401 is installed and the transmission

sequence number is lower than 3.491.853, then please create a PTSS.

If the fault code is no longer present, perform the following test steps.

Step 1: Check auxiliary oil pump connector and fuse

Step 2: Check supply voltage

Step 3: Check CAN lines

Step 4: Check VGS software and update if necessary, then continue with step 5

Step 5: Visual inspection of check valve; the valve is located in the torque converter housing (see pictures in attachment)

If the check valve is damaged, the torque converter housing and the auxiliary oil pump (component M42) must be re-placed.

Step 6: Replace auxiliary oil pump

If one step resolves the problem, it is not necessary to continue with the remaining test steps. Exception: After step 4 always perform step 5.

Symptoms

Control unit/fault code