- Engine Vacuum Leaks: All four of these codes can indicate a vacuum leak somewhere in the engine system, leading to incorrect air/fuel mixture ratios and misfiring.
- Oxygen Sensor Issue: Codes P0153 and P0171 are related to oxygen sensor malfunctions. A faulty sensor can cause incorrect fuel mixtures, leading to misfiring and emissions issues.
- Ignition System Issues: Code P0304 specifically points to misfiring in cylinder 4. This could indicate problems with spark plugs, ignition coils, or fuel injector issues in that cylinder.
- EGR System Problems: Code P0401 is related to the Exhaust Gas Recirculation (EGR) system, which helps control emissions. A faulty EGR valve or related components can cause the engine to run rich, leading to misfires and emission issues.
Diagnosis: To diagnose the specific cause of these codes, further testing and inspection are required. A technician would need to perform diagnostic tests, such as checking for vacuum leaks, examining the oxygen sensors, testing the ignition system, and evaluating the EGR system.
Repairs: Depending on the underlying issues identified, the repairs may include fixing the vacuum leaks, replacing faulty oxygen sensors, addressing ignition system problems, or resolving EGR system malfunctions.
