Quote: Hey guys the problem is the newer car electrical system if I understand correctly are what they call a CLOSED LOOP system where earlier cars had a openloop system. so when you unhook a new car battery while it running you taking a comoponet out of the circuit!! am I correct on this??
Open and closed loop refer to a state the vehicles electronic engine controls are operating in. In a nutshell, open loop means the car is running off pre-programmed parameters that would be close to ideal. They typically operate in open loop during warmup , which is basically until the oxygen sensor comes online. It might not allow the trans to shiift into overdrive etc.. Each manufacturer has different ideas.
Closed loop is when the computer will make appropriate changes to the operating parameters when the vehicle is warmed up and the oxygen sensor is sending logical information to the ecu.
When the O2 sensor reports logical information to the computer, it will adjust fuel injector pulse widths (amount of fuel the engine sees) to keep the vehicle operating close to ideal fuel/air ratios. That's what is called closed loop.
additionally, most cars are using heaters in the oxygen sensors to help get them online sooner. Also to cope with 02 sensors mounted downstream in the exhaust system (post catalytic converter) They may run too cold there.
keep in mind during all of this, an oxygen sensor may be reporting a signal thats "skewed" enough to change the ideal fuel mixture for the situation. The computer sees a signal thats relatively normal, and continues on like everything is fine. This is when things get harder to diagnose. Keep in mind, if the computer sees an illogical signal, that just cant make sense, it realizes this and turns on your check engine soon light. The computer saves this data, and in post 96 cars, saves a whole freeze frame of everything the computer is monitoring. Your speed, what gear youre in, how far the throttle was depressed etc..
Open and closed loop are not actually what we are discussing in this situation, but I hope that helps your understanding of it! I can get more in detail if you desire.
