QuestionI am having troubles with my car. I own a 2004 Hyundai Elantra Gls GT and the CEL light is on. I took it to a parts store so that they could read the computer and it popped AF Sensor fail. They then unhooked the computer and then started over. They got the same reading again. I am wondering if I need to replace the sensor and if so will this fix the problem.
I also was thinking about if I should replace the air intake with a newer or better kit. I am stumped because if I unhook the sensor it idles down but the light remains on and if it is hooked up the light is on too. Is it in my best interest to replace it and bite the cost in the butt or should I just fix what the computer says is wrong and go from there.
AnswerHi, Brian. There are two sensors commonly referred to as AF sensors. One is the air flow sensor, and the other is the upstream oxygen sensor (also referred to as the air/fuel ratio sensor). I'll need to know two things to help you:
1. The numerical code output by the engine control module (ECM). The ECM cannot tell you that whether the sensor is the problem; it can only tell you that it doesn't like the readings. In many cases, the numerical code will tell me additional information about what specifically the ECM doesn't like about the readings. This, in turn will help me sort out potential causes for the problem and advise you on how to determine the root cause or on the probabilities of different causes if difficult for a do-it-yourselfer to diagnose.
2. Even if you cannot tell me the exact code, knowing the sensor to which you're referring may assist me to a very small degree.
You should not expect that changing your air intake will do anything to repair the problem. In fact, it may make it worse. In terms of the ECM's ability to properly manage your fuel system, there is no intake better than the one that came from the factory. This is the intake that the fuel management was designed around.
