Tech Tip: Mercedes-Benz Battery Dash Light Illuminated – UnderhoodService

Tech Tip: Mercedes-Benz Battery Dash Light Illuminated

A Mercedes-Benz owner may complain that the vehicle's battery/alternator "visit workshop" light on dash display is illuminated. Use a scan tool to perform guided tests. This alternator is internally regulated and is connected by a LIN bus to the PCM so that the regulation control can be intervened.

Affected Vehicles: 2003-’05 C230 1.8L, 2003 CLK320 3.2L, 2006 C230 2.5 and 2007 CLK550 5.5

Customer Concern: Vehicle’s battery/alternator “visit workshop” light on dash display is illuminated.

DTC Tech Tips:

P2062: Generator or regulator is faulty — output is too low. There is no connection to the ECU.

P2061: Alternator serial interface — electrical or mechanical fault. Default operation of the alternator when the LIN bus fails is 14.3 volts. The ECU will send a signal of circuit 61 operation over the engine can bus or via signal line to the Signal Activation Module (SAM). Be aware some rebuilt alternators are not rebuilt with OEM-quality components.

Tests/Procedures:

1. Connect an alternator tester to the vehicle and test the alternator’s output amps and voltage.

2. Perform a battery load test.

3. Remove and inspect the brush set for sticking brushes. Inspect wiring on the back of the alternator for damage.

4. Use a scan tool to perform guided tests. This alternator is internally regulated and is connected by a LIN bus to the PCM so that the regulation control can be intervened.

5. Verify Battery Positive Voltage (B+) at the battery connection on the alternator; verify that it has a good connection. Some engines will have an in-line fuse from the starter to the alternator.

6. Test the wiring for a signal line between the engine control unit and the front SAM, if applicable.

Courtesy of Identifix

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