What are the reasons for the check engine light and vtm 4 light coming on in a 2005 Honda Pilot?

As is the case with any vehicle, there could be various reasons why the check engine light might turn on in the 2005 Honda Pilot. However, the VTM4 light does help to pinpoint the issue a bit. To properly identify the specific problem, you must use an OBD-II scan tool to check for diagnostic trouble codes (DTCs). If you don't have one, these tools are often available for free at most auto part stores. One common starting point is that issues with the oxygen sensors, whether upstream or downstream, can trigger both lights to come on at the same time. While this is not the only possibility, it is a frequent one, so it's important to still check your codes. If you come across P0175 during the scan, then it's highly likely that an O2 sensor is the culprit. Otherwise, use the DTC as a starting point for your diagnosis and proceed from there.