Notes for vehicles with catalytic converter - AH49.10-P-1000-01A

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2011 Mercedes-Benz ML350, 2010 Mercedes-Benz ML350, 2009 Mercedes-Benz ML320, 2009 Mercedes-Benz GL320, and 2008 Mercedes-Benz ML320. However, it is still accessible from the selected car via links, so may be relevant.

All engines with code 620a

Ignition faults

In the event of ignition faults the catalytic converters are endangered, since the fuel/air mixture is converted in the hot catalytic converter. If severe ignition faults occur, the engine may only be operated briefly at low load. The cause of the damage must be eliminated immediately. In case of doubt, check the catalytic converters for thermal damage after eliminating the fault in the ignition system.

Checking catalytic converter system for thermal damage

The catalytic converter is damaged by thermal overload. This can be checked by a visual inspection when the exhaust system is removed. Complaints about performance after engine malfunctions indicate thermal overload of the catalytic converter. Residues of the molten catalytic converter plug up the exhaust pipe.

Fuel additives

These should be rejected on vehicles with catalytic converters. It should be borne in mind that only the specified fuel quality may be used.

Use of leaded fuel

If leaded fuel has been used inadvertently, the function of the lambda control should be checked. If the probe is defective, it must be replaced. If the emission value is exceeded, replace the entire catalytic converter system.

Engine oils

The same recommendations (approved products, oil change intervals, etc.) apply for vehicles with catalytic converters as for those without catalytic converters.

Unpleasant odors

Hydrogen sulfide can form in the catalytic converter as a result of deposits from sulphur constituents in the fuel. Hydrogen sulfide causes unpleasant odors even in the smallest concentrations, however it is not hazardous to health.

Danger of fire (stopping off highway)

The catalytic converters are thermally insulated to ensure efficient emission control under all operating conditions. Therefore when the engine is operating correctly the temperatures are not higher than with conventional muffler systems.

Excessive temperatures occur only when unburned fuel/air mixture enters the catalytic converter (e.g. due to fault in ignition or injection system).