2003 Acura TL Misfire Codes P0300-P0305 and P1399: Fuel Pump or Engine Issue?
While driving, my 2003 Acura TL began sputtering and the check engine light started flashing. The onboard diagnostic system shows multiple misfire codes: P0300 (random/multiple cylinder misfires), P0302, P0304, P0305 (individual cylinder misfires), and P1399 (communication error with the powertrain control module). These codes indicate engine misfiring across multiple cylinders. I'm wondering whether this is more likely due to a failing fuel pump or a problem with the engine control unit (ECU). Any technical insights or diagnostic steps would be greatly appreciated, especially for a 2003 Acura TL with up-to-date maintenance history.
The most likely cause is an ignition system issue. Use an OBD-II scanner to review the freeze frame data and examine fuel trims (FTs) as well as oxygen sensor voltages. Inspect spark plugs for wear or damage and check for proper spark. Regarding a failing fuel pump, analyze the fuel trim values—abnormal readings may indicate fuel delivery issues. Perform a fuel pressure test and conduct a pressure leak-down test at key-on engine-off (KOEO). The ECU is typically not the primary suspect in such cases. Please confirm that all maintenance—including timing chain, air filters, spark plugs, and oil—has been performed regularly and that there are no aftermarket modifications installed.