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Clearing Computer Codes (97 Hyundai)

I recently did some work on my 1997 Hyundai Elantra… fixed some cracked vacuum lines, etc after diagnosing an EVAP problem (I traded someone with a scan tool some bottles of homebrew to read the codes!)

In my 1994 Toyota truck, clearing the codes was never a problem… I just pulled the EFI/ECM fuse for 30 seconds. (In fact, you didn’t even need a scan tool to read the codes!) In reading the Haynes manual for this car, it says to never clear the codes in this way as it will reset the computer and it will have to be “set up” by a scan tool.

I’d just like to know if reseting the codes by pulling the correct fuse will really screw things up, and if a scan tool is really needed to reset the codes.


Some places will read and reset them for FREE. Try Autozone or Advanced Auto Parts.

You can just pull off the negative battery terminal for a few minutes. It will erase the computer’s memory (and your radio’s, but oh well) and the CEL will be gone. Or, you could give a bit more homebrew to the guy with the tool and have him do it with his scanner - it takes less than half a minute.

This hardly qualifies as “research” since I only talked to 1 person, but I went to Advanced Auto yesterday and an employee said that clearing the codes by pulling the battery on some cars will seriously screw up a computer and it will need to be set up again by a professional. When they change batteries they hook the car up to a booster pack to avoid causing a potential problem. Since this advice also occurs in the Haynes manual, it sounds convincing… I’ll reset the codes with their scan tool once I finish the repairs to the evap system.

(Incidentally, I found some cracked hoses, and a malfunctioning 2-way valve. If its only supposed to let gasses flow in one direction, why is it called a 2-way valve??)

What you were told at Auto Zone (and, in the Haynes) seems correct. According to a Hyundai Technical Service Bulletin 06-40-005, dated March 2006, disconnecting the battery will require using a specific Hyundai scan tool to reset Adaptive Values.
Use any scan tools to erase the DTC (Diagnostic Trouble Codes). Disconnecting the battery will erase the Adaptive Values, which are something different.

According to, it seems that particular TSB has to do with the automatic transmission. My car is a '97 and has a manual. I’m going to play it safe and reset the codes with a scan tool once I have everything back together (waiting for a part). Are the adaptive values used in any of the car’s other systems besides the A/T?

you’re safe unhooking the cable,and you are correct adaptives pertain to auto trans only,some cars need the idle re-learned,your car does not.some lose nav,ect. your are safe.