Q: Can the fact that my long term fuel trim is -1.6 and short term is -2.3 be the cause of a P0422 on my 2000 Hyundai accent?

Hi Ashley. Thanks for contacting us today. The fuel trim numbers might be a symptom of the error code you are receiving, but not the source of the code. The P0422 OBD-II trouble code suggests that the catalyst efficiency is below the normal threshold in the first engine bank, which is generally the bank that houses the number one cylinder. The efficiency of the catalyst is determined by the powertrain control module (PCM), which uses exhaust and temperature information from both the upstream and downstream oxygen sensors to decide on the efficiency. When the readings from both sensors are determined by the PCM to be too similar, then the efficiency of the catalyst is likely below threshold, and the P0422 trouble code will be triggered. Usually a damaged or full catalytic converter is the cause.