Q: P0170 and P0173 codes. Mercedes-Benz w203 V6 C230 2006 year sport-sedan

You’re right to check for vacuum leaks. Low fuel pressure could also be a problem. P0170 and 173 refer to fuel trim on bank one and bank two. The ECU has detected that the engine is running lean, and is compensating by increasing the injection time in order to add fuel. When the ECU has added as much fuel as it can, and still sees the engine running lean, a P0170 and 173 will present. As you have said, the MAF can be a problem, and frequently is, without presenting other symptoms. An experienced technician can check the MAF using the live data feature on the diagnostic equipment, but the usual method for diagnosing the MAF is replacement with a known good unit. There are a number of other problems that can cause these codes including air leaks under the intake manifold, oxygen sensors, and poor electrical connections. Searching out the cause of a P0170 173 can be frustrating because the Mercedes system is so sensitive. If you decide you need professional help with this, contact Your Mechanic to have a technician come out to your home or office to diagnose your Mercedes and let you know what can be done to help.