Need help with check engine light

[GalaxyBlackEsky]

Well my check engine light came on a few weeks ago. So yesterday I put on a code reader and it wouldn't pull a code for me. So I have a question I got the code reader from a budy of mine and didn't really get instructions with it. Anyone that has used one what are the steps of doing it. I just want to make sure I am doing it correct.

Thanks

 

[badtothe bone]

I find several things very alarming here.

One is that the light came on and you refused to pull over and find out what the problem was and two that you refused to have the problem diagnosed or repaired by a trained technician. Stores such as Pep Boys will scan your vehcile for you for free. Most of those people, although not certified as mechanic's or properly trained to diagnose your problems can usually give you their opinion as to what your problem may be - since they do it all the time for people like you.

Most codes that flashes a check engine light usually involves the emissions, due to the fact that your vehicle will still run even when the light is on.
But the problem is that even though it runs, the computer usually puts the vehicle into the limp mode and it will run rough and get terrible gas mileage.

Most scan tools works on the precept that you plug the tool into the port under the dash board. You then turn on the ignition key to the on position - but you do not start it. Once the scan tool recognizes the port, it will go into a main menu and will ask what you care to do.

By pushing the read codes button, it will display the first code in the computer. Your job is to write that code down on a piece of paper. Then procede to read all the other codes in the computer. When you get to the end of the codes, the computer will ask you - do you want to erase all codes.

Your answer should be YES!

Because of your refusal to have the vehicle properly diagnosed when the light first came on. You might find that you have codes that has nothing to do with the origional problem. As you drive in the limp mode, other codes will surface ( snowball) the longer you drive it.

Just think of the LIMP MODE as walking on a fractured leg. If you were on the top of a mountain, with no way down except to walk, You could walk on a fractured leg, it might not be pleasant and you might not make good time and you could do more damage to the leg and the bone the longer you walked on it, but you could walk. At the same time, you could not run a marathon or play professional football with a broken leg. That is how the LIMP MODE works.

Usually the LIMP MODE will involve advancing the timing of the ignition and making the fuel mixture rich so as not to damage the engine while you drive it in that mode.

There are some very common / ordinary codes that usually surface once you clear the codes. In the old days, the most common code was for the oxygen sensor. Today most oxygen sensors will go for 100's of thousands of miles as long as you do not put fuel injection cleaner ( junk ) in the gas tank. Most oxygen sensor codes are now triggered by a faulty catalytic converter.
Low voltage or two sensors that has the same readings - which triggers a code which will say that catalytic converter below nornal threshold.

The second set of codes usually involves a sensor on the motor, the trick is knowing which sensor it is.

The third set of codes usually involves a leak in the fuel system. Be it a hole in a line, hose, a hole in the gas tank or a bad purge solenoid valve or evap cannister. If that is the code, the vehicle will still run and might not even go into the limp mode, but the light will come on every time you go to wide open throttle and everytime the tank falls below half full. It is a very dangerous situation and is almost never due to a loose gas cap or bad gas cap. For the most part - that is just wishful thinking.

Usually it will involve going to a GM garage and having the problem diagnosed and might involve using a sniffer to find the leak.

Either way, most of these repairs cannot be done by a shade tree mechanic with a cheap set of tools. Even a good / cheap scan tool that reads and clears the codes might be $150 or more.

Read the codes and come back and tell us what they are.

 

[GalaxyBlackEsky]

Thanks for the info but actually I haven't really driven the car since the light came on. I work from home so maybe I have driven it 100 miles since the light. But car runs fine since the light came on. It actually came on right after I got my Magnaflow muffler put on. I was thinking it could be a o2 sensor maybe from welding the muffler on could have done something to them. But I have a Creader Launch ODBII code reader and when I plug it in it just flashes LAUNCH then goes ---- and returns a E and recycles through the same steps. I have tried to disconnect the battery and tried it again and same issue and the check engine light will come on right away. Also I noticed that I guess if the check engine light does come on you cannot remote start the truck. I have a appt tomorrow with the dealership anyway so hopefully they will find the issue. I just have a feeling that it is going to be the O2 sensors.

 

[badtothe bone]

OBD II - on board diagnostic's, cannot be cleared by removing the battery terminals. That was something that only worked on the earlier version of vehicles.

Before OBD II - you had a plug for each manufacturer and computer for each vehicle. A technician / garage had to have on hand a computer program for every year, make and model of car and a plug to adapt their scan tool to the port. I had a Snap On scan tool for years and it cost about $500 per a year - just to buy the updates and plugs.

Finally the manufactures all got together and agreed to one simple plug and one simple program for all vehicles. I will not say that it was all a scam, because the earlier vehicles usually had terminals that could be jumped, where a light in the dash board would blink and you could count the blinks and figure out which codes were coming up in the computer. Those computers could be cleared of their codes by removing the battery wires and maybe even dead shorting the terminal ends on the wires together - which would remove the residual power which was held in the memory - usually in a capacitor.

The OBD II did away with all that, but required you to have a scan tool to read the codes and to erase the codes from the memory.

Power tuners are a poor substitute for a scan tool.

Changing the program from the origional or upgrading your exhaust to a aftermarket - could void your warranty. What that means is that it could cost you mucho denero.

One little guess - is that the aftermarket exhaust did not have bungs for the down stream O2 Sensors or that they were damaged when they were removed or that the mechanic who did the work removed the cat's.

You are there and I am here and I am just taking wild guesses as to what your problem is - without the proper codes and not being able to see your vehicle or know what you did to it, would be like me calling a physician and asking him / her over the phone - what is wrong with me? - without describing the problem and without a office exam - it is pretty tough.

100 miles isn't going to hurt it, and driving without the down stream sensors will not hurt it either.


Here is some of the codes
http://www.obd-codes.com/trouble_codes/

 

[Eagle]

OBD II - on board diagnostic's, cannot be cleared by removing the battery terminals. That was something that only worked on the earlier version of vehicles.


http://www.obd-codes.com/trouble_codes/

Actually man, MOST vehicles OBDII codes clear with a battery disconnect also. I have cleared so many misfire codes, o2 codes, and maf overrun codes by unplugging a battery it isn't funny.

Some that don't are: Volkswagens, late 90s Nissan sentra.

Those require a drive cycle with no error to clear the code without a scanner.

A drive cycle might be x miles at ___ mph or greater with A/C on, x miles at ___ mph with a/c off, x minutes idle ac off, x minutes a/c on idle, x minutes at speeds between ___ and ____ mph... I nothing that is particualarly HARD to do, but inconvenient enough the code will stay illuminated for a while.

And BTW, Autozone etc will no longer CLEAR the codes for you anymore. Yo uwant them cleared buy your own scanner, or ask the guy to look the other way while YOU push the erase codes [yes] button.

Upgrading your exhasut would not be a warranty violation either.