Electrical - Vehicle Doesn't Perform Automatic Engine Stop

Mercedes Benz C 250 (204.052) (CANADA) V6-2.5L (272.921) Technical Service Bulletin # LI54-10_P-053538 Date: 120405

Electrical - Vehicle Doesn't Perform Automatic Engine Stop

Vehicle does not perform automatic engine stop

Topic number LI54.10-P-053538

Version 1

Page 38

Design group 54.10 Battery, voltage supply, voltage converter

Date 04-05-2012

Validity Model series 169, 245 with code B01

Model series 204 with SA code B03

Model series 172 with SA code B03

Reason for change

Complaint:

The vehicle does not perform the automatic engine stop although the ECO function was activated via the ECO button.

Cause:

Battery sensor transmitting incorrect temperature value

The temperature value and/or voltage value transmitted by the battery sensor is constant and does not change

Remedy:

IMPORTANT:

- On no account should the sensor be de-energized prior to the test, i.e. do not disconnect the ground terminal on the battery, otherwise a reset

will occur and the result of the function test will be inaccurate.

- Sensors that previously transmitted a constant temperature value could then become OK temporarily, i.e. the fault will not be rectified!

Function test of battery sensor:

a) Check the temperature value:

A battery sensor that transmits a constant temperature value of -40锟斤拷C or +120锟斤拷C must be replaced.

A battery sensor that transmits a constant value between -40锟斤拷C and +120锟斤拷C must be tested as follows:

- Required aids:

- Xentry

- Multimeter capable of measuring temperatures

1. Measure the ambient temperature at which the vehicle has been kept for some time (e.g. the outside temperature if the vehicle has been

standing outdoors for some time)

2. Measure the outside temperature of the battery on the negative terminal clamp directly at the IBS using a suitable measuring instrument

3. Using Xentry, read out the current battery temperature: - Select BSN - Battery sensor (B95) # Current data of battery sensor # Battery

temperature

- Compare these three temperatures, the ambient temperature, the temperature at the battery negative terminal and the battery temperature (from

Xentry), taking into account a tolerance range of +/- 3锟斤拷C.

- Repeat the test after approx. 30 mm in order to rule out delayed reaction of the battery sensor to temperature changes.

If the value transmitted by the battery sensor is outside the tolerance, the battery sensor must be replaced.

b) Check the transmitted voltage value:

- Start the engine. Does the voltage value measured by the battery sensor change?

- If the transmitted voltage value remains constant, the battery sensor must be replaced.