Expert: Sean Halliday - 10/9/2010

Question
QUESTION: my 2003 mercedes benz s500 4matic won't start and there is ESP warning in instrument cluster.

ANSWER: ESP,is the electronic stability system.When you say will not start,does the engine crank over?

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QUESTION: yes the engine cranks.

ANSWER: First thing to do is determine if it has no spark or fuel.Test fuel pressure at the rail and using a spark tester to see if you have a good spark at the plugs.

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QUESTION: could it be the mass airflow sensor.

Answer
Could be many things, so as i said determine which is at fault,fuel or spark as it will be costly to try and guess what part has failed.The MAF sensor will not cause a no start.You may need a shop to look at this as there is no way to verify spark, without a strobe, or fuel pressure,without the proper fuel pressure tester.