My 2002 slk 230 kompessor has been giving me a 301 error. so I changed the spark plugs. No help, changed the #1 coil pack. After running very well for 1 week I get the p0301 again.
Could be injector, plug wire, ignition module, wireing
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back. I know this tool can do your car, http://chinasinoy.com/wholesale/mb-star-c3-pro-with-seven-cable-for-benz-truck-and-cars-fit-all-computer.html If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.
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