2007 Chrysler 300 P0300, P0507, P2173 Fault Codes - Random Misfire and Limp Mode After Maintenance
I recently completed a major engine service on my 2007 Chrysler 300, replacing the water pump, timing belt, tensioner, and EGR valve. The car ran smoothly for nearly a month afterward. However, I now have persistent fault codes: P0300 (random misfire), P0507 (exhaust pressure too high), and P2173 (fuel trim issue). These codes trigger limp mode, severely limiting acceleration. I’ve tried the ignition switch reset procedure to bring up the codes on the instrument panel, but I’m unable to locate any vacuum leaks. The random misfire suggests a possible EGR valve issue, as this code typically points to unexplained combustion problems across cylinders. However, I'm concerned that the timing belt might be faulty despite proper installation. I need expert advice—this is significantly impacting my daily driving and I’m hoping for a clear diagnosis without costly repairs. Any insights into how these codes are related or what diagnostic steps to take would be greatly appreciated.
First, perform a full OBD2 scan—some fault codes may not appear in limited mode. The P0507 and P2173 codes are likely contributing to the P0300 random misfire. A high exhaust pressure (P0507) can disrupt engine timing and fuel delivery, leading to misfires. To check for vacuum leaks, use the classic 'carb cleaner spray' method: spray carb cleaner at suspected vacuum lines or connections. If you hear a change in engine sound or notice a spike in RPM, that's a leak location. Clean the throttle body thoroughly—avoid using an oiled air filter, as this can worsen fuel trim issues. Consider performing a throttle body relearn after cleaning. Did you unplug the throttle body during maintenance? If so, ensure it’s properly reconnected and relearned.