DTC code question?

[jasonvibe]

I had a code. It was cleared by the dealer but no repairs were done. It has not come back. I will go into details later. QUESTION:If I have a code and it is cleared with a scan-tool. But held in the ECM memory. Can it come back if the conditions cause the same problem code? Or does the power have to be removed form the ECM to empty the memory before it can give a CheckEngineLight again for the same thing?

[northvibe]

the CEL (check engine light) should come on if it senses that issue or another issue even if that same one was cleared. Otherwise that could be a big safety concern :s

[Mavrik]

if its cleared with a scan tool like a GM TECH II then its gone for good unless the issue that caused it to set in the first place returns and resets the code.

[jasonvibe]

OKAY, so no matter what.You have to get a CEL for any valid issue. No such thing as not allowing a code due to a "repeat". OKAY...so does anyone know the code for a loose gas cap? I suspect there could be many. thanks in advance...

[joatmon]

Quote, originally posted by jasonvibe »OKAY, so no matter what.You have to get a CEL for any valid issue. No such thing as not allowing a code due to a "repeat". OKAY...so does anyone know the code for a loose gas cap? I suspect there could be many. thanks in advance... You can have a problem and still have no CEL (ask pmh013 )I think a CEL means that there is a problem, although some people think they are no big deal (CELs after CAI install seems not uncommon, but I thnk CELs should be fixed so you know if some other more serious problem occurs.THe car's computer ris monitoring a lot of things, and tests things to make sure they are ok. CELs all have some criteria to be set, and there is also a criteria to be unset. For example, if you leave the gas cap off, the car goes through a couple of cycles to try to put a vacuum on the gas tank, and after so many tries, it lights the CEL to let you know something is wrong. If you put the gas cap on, and don't clear the CEL with a tool, after a while the car will go through some number of other test cycles and will notice the problem seems to be fixed and will turn the CEL off. If you had a CEL because of a loose gas cap, you screwed the cap on correctly and the code was cleared with a tool, then you should be fine unless you leave the gas cap loose again, or some other problem comes up. If you clear the code with a tool but don't fix the problem, then after some number of test cycles, the car will light the CEL again. If you fixed the problem but didn't clear the code, it would probably go off by itself after a while, how long depends on how and how much you drive the car.For some of the CEL codes, the test to light the CEL is a lot quicker than the test to turn it back off if the problem is not repeated. Clearing the code with a tool and then waiting to see if the light stays off can be a quicker way to figure out if whatever was done to the car actually corrected the problem. If there is a problem that causes the CEL to light, clearing the code just clears the code, turns the light off. , if the problem is still there, the light will light up again. I cleared my P0420 for a bad cat a dozen times before I fixed the cause by replacing the cat, and no light since, ~40K miles (knocks wood)A single problem can set multiple codes at the same time. When my pickup threw a CEL (because of a bad battery cable, weird voltages caused all kinds of things to act up) my code reader had a half dozen codes in it, a wide range of potentially costly possible causes (luckily, all fixed with a cheap replacement cable clamp)I think the codes that a loose gas cap can cause are mostly in the evaporative emissions test, P0440 P0441 P0442 P0446 and maybe some others as well.The other thing to keep in mind about CELs in these cars is that if the light comes on and stays on constant, then it is most likely a lower priority problem, still something that you should correct, but perhaps something relatively safe, like maybe polluting more than you should, a lof of CELs are related to emissions control. SOme however, are for more serious problems, and if the CEL flashes, that means it is a serious problem, and you should probably turn the engine off until you figure out what is going on, or risk some kind of serious damage.

[jasonvibe]

I was sure it was a 400--- but the dealer said I got a 133. The MATRIX book says to me it could simply be the O2 sensor in the manifold.Or other emissions evap thingy. Dealer showed me there was a bulletin to change the intake manifold gaskets if a 133 appeared. I know these to be o-rings on the manifold. I should not be needing such a repair unless the manifold is bad out of the factory. To which new orings are only a temporary soltuion. He said they would check it with a straight edge when the job is done....keep reading...I'm thinking, If it is bad the problem should come back. Also in the manual it could be one of the purge / vacuum things in evap system. I am hesitant because this guy for some reason removed my oil filler...reason unknown.The mech did not put it back in place. Which on my trip home resulted in a OILED engine and fire wall and lots of smoke. I found the filler on the rubber edge above the firewall. He had the car in the shop for all of 20 minutes and this is what I get. I informed them of my disappointment. To which they steam cleaned the engine. WOULD you trust these guys to remove the intake manifold unless someone was absolutely sure the O-rings were a cause? So I told them I wish to wait till it reappears. Been a week, has not come back. The car runs perfectly. Any ideas?...PS- your cat should have been covered for free. AND what does pmh013 know?

[ColonelPanic]

Quote, originally posted by jasonvibe »AND what does pmh013 know?Quite a bit, actually - just search and see what trouble she had been through, all thanks to crummy Toyota cats! And crappy AWD components too, but that's another story.

[jasonvibe]

1st. ON any car with a diff at the front or back. It is absolutely foolish NOT to change the gear oil at least every 30k. He even admits he went way beyond the recommended 60k miles. Me, I changed the gear oils in my last 4wd truck evry 2-3 years or 30k. This animal will be seing it's 1st rear gear oil change this year at 24k . I have already done the front because it is under the most load. I use the best oils I can find. I am researching whether synthetic is safe for the rears on these clutch systems. HIS CAT issue is what I hope is not the norm. I am close to 20k miles. Cats plugging up is usually due to oil burning. They should have pulled the sparks plugs for a look when it happened the 1st time. My car runs like new. Extended warranties do you no good without a good dealer. If I have his problems in the future...I will not buy another GM or possibly Toyota.

[joatmon]

I guess pmh013 had a several issues with the car, but I was referring to her troubles with catalytic converters. She had problems with loss of power, poor fuel economy, which turned out to be a clogged catalytic converter. dealer replaced the thing, and the problem happened again, another clogged converter. I think it may have even happened a third time. One issue si that the dealer never corrected whatever was clogging the converters, but the relavant point to this thread is that through all of that ordeal of having troubles with the car, having failed parts replaced mutliple times, having serious driveability issues, she never had a CEL come on. I only mentioned it in htis thread to say that you can have a problem with your car that will not cause the CEL to come on.