2010 Mercedes Benz C 300 (204.054) V6-3.0L (272.947) Page 26

The message from the auxiliary oil pump is not available on the CAN bus.

Possible cause:

- M42 (Electric transmission oil pump) / N89 (Transmission oil additional pump control unit)

Affected functions:

- Engine start

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Test 1: Check component M42 (Electric transmission oil pump).

1. Check component M42 (Electric transmission oil pump).

Operation number of operation texts and work units or standard texts and flat rates:27-0641Test prerequisite

- Battery voltage is OK.

Test sequence

- Switch off ignition.

- Disconnect connector at component N89 (Transmission oil additional pump control unit).

- Use multimeter to check voltage directly at jacks of wiring harness for component N89 (Transmission oil additional pump control unit).

- Switch on ignition.

Measure direct voltage with multimeter between 1 and 4Specified value

- Voltage [8,5...16,4] V

Question

- Is the measurement value OK?

YES

The measurement value is OK.Further test:Test CAN wiring for Open circuit.Test sequence

- Switch off ignition.

- Disconnect connector at component N89 (Transmission oil additional pump control unit).

- Expose component X30/21 (Drive train CAN voltage distributor connector).

CAN bus HighMeasure resistance with multimeter between (X30/21) 2 and (N89) 3CAN bus LowMeasure resistance with multimeter between

(X30/21) 1 and (N89) 2Question

- Is there an open circuit in the CAN bus lines?