Engine light - does it turn off by itself?

I will also say thanks for this explanation, as it does make sense to me. Much appreciated. Tomes

You're welcome! Sorry to be so long-winded.

Nah, long-winded is good. It covers it all.

By the way I went and got the Haynes manual today. In there it tells ma how to check the coils. It says to use an ohm meter to check the primary and then the secondary resistances. If they are not in the range they give then it needs replacement. Looks like the project for this weekend.

And Jeff - if you see this - I looked at OBD II readers at Autozone today. The cheapest one at $70 reads and resets the codes, just does not display what they mean (which I could just look up anyway). The more expensive ones offered things like other languages, battery power and stuff I don't think I really need. It looks like the one for little old me. Do I need anything besides reading and resetting? Tomes

I have the most inexpensive Actron OBD II code scanner and it is usually good enough for me. It does not read manufacturer-specific codes, tell whether the ECM is in ready state, freeze frame data, or show actual signals from sensors, which would be handy. I can read sensor signals with a volt meter, and if you have a higher end volt meter, you can freeze data with it. My scanner does read SAE generic codes and can reset check engine lights.

I have to admit ive read a few manuals (not toyota specific) that suggest a re-learn process is required. Also a friend of mine is doing some idle-speed research on a ford engine/ecu system using individual cyl EGT/AFR sensing and has noted a definite "settling period" after a battery replacement.

that seems to be all the time - if i run the car from reset on high octane fuel i get a very spritely car. As soon as i switch to normal fuel and boot it once its loses oomph and never regains it until after another reset with good fuel.

I guess my long-winded post was really a clarification between re-learning "engine parameters," which I consider to be the base information for the engine to function, and, for lack of a better term, "optimizing parameters."

the only thing I remember that the engine stores is ignition timing. BTW, if you go back to higher octane fuel, the timing should advance again after

Yep, that's the one Autozone has. Thanks for the thoughts, Ray, much appreciated. Tomes

There is a little catch to owning an OBD II code scanner, and that is that friends will ask you to check codes for them. Of course, when you plug in a device that looks pretty sophisticated with blinking lights and flashing numbers, those friends will expect you to diagnose any problem in the car with it. My daughter said that the OD off light was flashing and the check engine light was on. The check engine light pointed to an O2 sensor, which was easy to check with a volt meter. Turns out the OD off light was not flashing, it was on solid because she inadvertently pushed the OD off button, which she did not know was on the shifter.

I am thinking that the friends will come flocking to me only if they know that I have the darned thing . I gotta decide how much of a secret this becomes....

By the way, the check engine light did indeed go off all by itself (I never got around to pulling the battery cable). I am supposing that it took somewhere between 20-50 starts (I am _so_ precise...). More accurately, it took about 2 tankfulls of gas, maybe about 700 miles or so. So I am supposing now that I indeed fixed my problem with the plug and wire changeout. If I still had a problem it would still be chirping codes at the light, right? Tomes

It won't stay a secret long

It was not the number of starts that turned off the check engine light (actually called a malfunction indicator light, or MIL). Most OBD II codes have 2-trip detection logic, which means that the system has to detect the presence of a problem on 2 consecutive trips to turn on the light and the absence of a problem on 2 consecutive trips to turn off the light. A "trip" has a specific definition with specific engine operating parameters, like starting after a cold soak, driving at a specified speed for a specified time, then changing the speed, cruising, etc. If you drive short distances, it may be a long time before you take 2 OBD trips.

OK, I understand this. I feel pretty good about this whole thing now, and we will see how it goes from here. I do want to thank you a final time for your help on this with all of the explanations along the way. This is indeed very cool of you and it much appreciated. Tomes

You are very welcome! I have enjoyed watching my dad work on cars since I was about 5 years old, I started doing simple work on the family car when I was around 14 like rotating tires, doing oil changes, changing plugs, points, and condenser, blowing brake dust out of drum brakes (oops!). I got a dream job working for an automaker right out of college, and even though I no longer am in the car business, I try to keep up.

Toyota introduced electronic fuel injection in the Supra and Cressida in