What Does the Code P170 Fuel Trim Malfunction Bank 1 for a 2003 Mercedes Benz C230 Mean?


The 2003 Mercedes Benz C230 was equipped with a DOHC 1.8-liter, in-line, four-cylinder supercharged engine that produced 189 horsepower and 192 foot-pounds of torque. The 2003 C230 came standard with air conditioning, power windows and door locks, and a six-speed manual transmission with overdrive. The 2003 C230 had an onboard diagnostic computer using the OBD-II system. The OBD-II system provides codes related to different faults that the vehicle is having. Diagnostic trouble codes is abbreviated as DTC.

What is P0170

  • Mercedes Benz OBD-II code P0170 is defined as "Fuel Trim Malfunction (Bank 1)." This means that the OBD-II computer picked up an error message relating to the air-to-fuel ratio controls, or that there was a computer control malfunction relating to the air-to-fuel mixture.

Symptoms of P0170

  • The P0170 DTC code can create different symptoms in the 2003 C230, beginning with the MIL or "Check Engine" light indicator illuminating. Other symptoms include the vehicle engine starting then stalling, poor fuel economy, black smoke from the exhaust, rough idle or misfire under load.


  • Causes of the P0170 code can include a vacuum leak, a bad oxygen sensor, oil in the electrical engine wiring harness or a defective mass airflow sensor. A defective mass airflow sensor is common for Mercedes Benz models that generate the P0170 code. The cam position sensor, crank sensor, ignition coils and oil sensor should be tested if the above stated items are not the cause of the DTC.

Recall 2008020002B

  • A recall pertaining to the generating of the P0170 code has been issued by Mercedes Benz. Mercedes Benz issued recall number 2008020002B on 08/26/2008. The recall is titled "Replacement Of Engine Vent Hoses," and pertains to a possible crack in the vent hose located under the intake manifold. The recall will require Mercedes Benz to replace the vent hose that is known to be faulty, as well as the engine check valve that is in-line with the vent hose. If you have not had this recall work performed, or are unsure of your vehicle's service history, take the C230 to your Mercedes dealer for an inspection and to have the recall work performed.

Recall 2009100001B

  • Mercedes issued a recall number 2009100001B pertaining to the replacement of the camshaft solenoid adapter harness. This recall pertains to the camshaft, and can cause the camshaft position sensor to generate a code. Take your C230 to your local Mercedes Benz dealership to have the 2009100001B recall work performed. This recall was issued on 04/01/2011, and requires Mercedes to replace the camshaft solenoids and the electrical harnesses, if they are found to be faulty.

Recall 2008070001A

  • Recall 2008070001A was issued by Mercedes Benz on 10/16/2009. This recall pertains to the engine control module or ECM. The ECM controls the air-to-fuel ratio, and can create the P0170 code if it is faulty. The recall requires Mercedes Benz to re-code the software calibration in the ECM, and the recall effects the 2003 C230.

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