A code reader such as one made by Acton is available from automotive parts houses such as NAPA, Advance Auto parts, and AutoZone. This code reader works on the OBD2 systems made on or after 1996 (not sure of the exact year).

There some caveats, however. Code readers available over the counter may not have all the functions that are in professional units, and one of those omitted functions may be the ability to reset the maintence light for the oxygen sensor. As I understand it, it is illegal to reset the maintence required light for the oxygen sensor without changing the sensor. The dealers and repair shops that I know will not reset the Oxygen Sensor code unless they change the sensor. I have one repair shop that will accept a sensor that you purchase, but they must do the install.

If your main reason for buying a code reader is for resetting the maintence codes, check to see if it has that capability before your purchase.

I have changed oxygen sensors and you are correct in that it is not difficult in most cases. It is best, though, if you have a special socket with a relief for the electrical leads.

Thanks jemdandy

It sounds like the O2 sensor is a bad actor...or because it has a strong influence on emissions the on-board computers used these days keep a "close eye" on that effect. It may be that on older cars/trucks I've had I drove them for years with a faulty O2 sensor and the inspection station never detected omission problems...but I think the one time I changed one it may have been because of a failed inspection result..too long ago for me to remember.

I had assumed the SES would automatically "reset" when the error was fixed, e.g., in this case the O2 sensor replaced.

The engine controller turns on the "required maintence" lamp for a scheduled replacement of the oxygen sensor. It does not necessarily mean that the sensor has failed. But, in your case you are reporting only 10,000 miles in 4 years and I am surprised. This is extremely low miles for a 4 year old vehicle. Normally, the scheduled replacement time for an oxygen sensor is on the order of 60,000 to 80,000 miles. Maybe your system includes a 'time' factor as well, or possibly, the sensor did fail.

When the engine controller sees an out-of-bound voltage from the oxygen sensor, it ignores it, sets a trouble code, and uses default settings which may be on the rich side. Thus the engine will continue to run, but may not pass an emission test (at the tail pipe), and your fuel mileage may be reduced. It will not pass the code reading part of an emissions check.

Thanks,

I didn't even look to see if there was some scheduled maintenance needed on the O2 sensor. The only interaction on maintenance I've had is changing the oil/filter and fluid levels, and they haven't needed any adds. The low mileage usage means I have only changed the oil once a year, the "oil life" computation never comes on, but I still have to reset that, and it is the only user reset supplied with the interface.

The cost of the dealer doing the work isn't a big "waste", but I had in the recent past used a local gas station garage for work on my older vehicles. He'd likely have done the work for a lot less, and I assume he has the code reader expertise to reset. Still, the 4 year point is a good point to give the dealer's shop a chance to look for troubles based on the full GM experience...besides, and sadly, we may not have a GM shop in the future. These are tough economic times.

Hmmm.

How much do you really want to know about the humble little oxygen sensor? Got a day or two to sit in a formal class?

The MIL will come on if the vehicles on-board diagnostics detect a condition that indicates that the vehicle "might" be polluting the air in excess of 1.5times the FTP testing for that vehicle platform. It does not have a scheduled maintenance for the O2 sensors at any mileage or vehicle age. The PCM's programming performs both passive and active testing for each and every sensor, as well as each and every component that the PCM controls. This means the O2 sensors, as well as every other sensor, and the sensors circuit. Just because you get a P0101, Mass Air Flow sensor performance, it does not mean you have a bad Mass Air Flow sensor, and the O2 sensors are not an exception to this.

In the event a single sensor fails, or appears to have failed, the vehicle actually does not rely on base programming any more. First it relies on the companion sensor for a "V" engine, and it also relies on the downstream sensor(s).

Otherwise known as a "LAMBDA" sensor, the one thing an oxygen sensor does NOT sense is in fact oxygen. A/F sensors as found on many smaller engines (growing numbers since 2002), and just about all across the board with 2006 and newer vehicles that the ability of the sensor to report the actual air/fuel ratio to ever higher levels. Previous to that, an oxygen sensor simply switched between a high VS low voltage output depending on whether the air fuel ratio was slightly richer or leaner than stoichiometric. "Stoich" is generally referred to be 14.67 to 1, but when fully understood, that is an average, and not a single exact number.

Top independent shops are not necessarily cheaper than the dealer, in fact it can be shown there is every reason to expect that they actually could be a higher price, and yet still a better value!

Aftermarket code pullers are the one thing that I have no experience with. As a full time tech, I understand that the code by itself is little more than the first step of the diagnostics. Pulling the code, and then throwing a part is not doing diagnostics, and repairs of a vehicle. Sure you can get lucky and the code will in fact identify a failed component. Try and work that way in a shop, and you'll quickly earn the reputation for not knowing what you are doing because of how often you would fail to repair a customers car. However if you did guess correct, and you replaced the part, you would then after driving the vehicle a few days when the PCM has had a chance to actively test the sensor and saw it pass the on-board tests two times consecutively, the lamp would in fact go out on the next restart and the code would then be stored to history. Then after another forty to fifty restarts if the code did not reset the code would be erased completely. (in most systems, only retrievable then on certain ones and the tech has to know how to go looking)

John_g

Thanks, good to see you are still on this forum and taking the time to provide welcome and useful tutorials. I don't post here often, but have gotten similarly good advice from you in the past.

Interesting on the independent (which you are) being possibly better than the dealer. I can see that could be the case for a experienced independent (such as you) who also keeps up-to-date. I think some are glorified shade tree mechanics, who were fine for cars back in the 60s. Then too, I suspect the dealer may have some "green" trainees who don't have a keen eye/ear or a vested interest in the shop surviving, well not as much as an owner.

I'll save a copy of your helpful note, for future reference.
I'm a old guy and figure with my poor sight, hearing, and mind it is best to have most repairs done, rather than DYI, but I still give it a shot once in a while...I installed my own trailer receiver hitch on the subject truck when it was new, and I haven't lost a trailer yet, but then I haven't driven many miles yet either.

I have the 2.8 4 cylinder with manual everything, the low-end truck. Consumers doesn't give the Chevy Colorado good grades on reliability... what's the experience on this forum? What should I look out for, other than the bad valves for which I have an extended warranty..to 7 years and I figured it could have been the cause of the SES light, but the dealer's shop said no, it was the O2 sensor and I can say the SES is no longer lite.

Thanks again, and keep up the good work for your customers who can't afford a new car because of the poor economy.

Many local DIY types purchased code readers shortly after New York added the OBDII test to the annual inspection.

People used to spend a small fortune in gas, wear & tear, lost time and lost work traveling to the discount auto parts stores for free code readings, paying garages for code readings and paying garages big bucks for relatively simple repairs.

Many of our customers with code readers use code readers, automotive manuals, mechanic's software and the internet to troubleshoot dozens of vehicles belonging to family, friends, neighbors, co-workers etc.

The flat economy has effectively forced many employment/income/savings/credit challenged people to become self sufficient electrical/emissions troubleshooters and/or forced them to use the services of unemployed/under-employed mechanics that work from home, or on-site.

I just fixed an intermittent electrical issue for customer that spent a small fortune with 3 different garages that failed to fix the problem.

Having a little knowledge also helps prevent customers from being taken advantage of by dealerships, independents, tire/brake/inspection outfits etc.

Many service outfits are getting pretty desperate for work judging by the amount of places advertising 99 cent New York State Inspections, free inspections and heavily discounted services.

Thanks 'mj..

I have been thinking along the lines you describe. In fact, when I turned my 2005 Colorado into the deal shop I listed two problems: Service Engine (must be fixed to pass NJ Inspection - I think NJ does not use the code reader, just looks at the dash Icn) and the Security fault. My truck is a basic model, manual windows and locks, no electronic security. The dealer shop was successful in getting the SES Icon off, and in applying two "silent" recalls (not happy I didn't get a notice), but the Security fault did not result in any action... I'm concerned it is a computer problem, expensive to repair. The problem may be that the Security fault isn't on all the time, so if I had a reader I could look when it is on. Still I think the problem would not be uncovered as the vehicle isn't equipped with anything that can be fixed.

Mark.

If there is one thing that annoys me more than anything else in this trade, it's the never ending line of people who tell the customers want they want to hear whether its accurate or not. Reminds me of the service manager that told one old lady that the fog that she kept finding on the inside of her car windows was a small coolant leak and we simply had to tighten a hose clamp, instead of telling her that as the vinyl interior cures it will give off chemicals that can fog the glass and it will go away completely by the end of the summer all by itself. I think I saw that car in to get the windows cleaned every week all summer long. What the service manager did was tell her what she wanted to hear, that something got fixed.

You wrote "I just fixed an intermittent electrical issue for customer that spent a small fortune with 3 different garages that failed to fix the problem. "

It takes four things to be able to fix a car. The right person, the right tools, sufficient training, and a broken car. Intermittent by nature are a car that isn't broken all of the time. If it happens to not be broken at the time that any of the other three shops saw the car, then they had no chance. Now keeping in mind what I started off with, people in this trade wanting to tell the customers what they want to hear, instead of the way it really is, you can go right ahead and fault the shops as you did, and play the hero card here. The facts are the forces at work inside of this industry that you allude to are going to hurt the consumer until we all learn how to be professional.

Quote" The flat economy has effectively forced many employment/income/savings/credit challenged people to become self sufficient electrical/emissions troubleshooters and/or forced them to use the services of unemployed/under-employed mechanics that work from home, or on-site"

Side work is stealing, pure and simple. Someone doing side work has no insurance, which a shop has to pay in order to protect the customer as well as themselves. They don't pay taxes which short changes everyone else that does. They operate in the street, or in a garage not zoned for the business, the list goes on and on. It's the classic apples to oranges kind of a comparison. You cannot compare what happens in someones back yard to what a real shop does today.

Quote "Having a little knowledge also helps prevent customers from being taken advantage of by dealerships, independents, tire/brake/inspection outfits etc"

Now where does one get this knowledge? In some back alley? Here on the Internet? You can find videos of people unlocking a door on the Internet with a tennis ball that has a hole cut in it. Its fake, but people want to believe it. Your response is IMO another tennis ball trick that unfortunately I don't have all day to debunk. Plus I have the disadvantage of having to tell it like it really is, not the sugar coated version that people want to hear as you did. Yes it costs money, and sometimes you might consider it "big bucks" for something that may seem relatively easy. Did you see Jerry's response just now?

Quote " and the Security fault. My truck is a basic model, manual windows and locks, no electronic security. The dealer shop was successful in getting the SES Icon off, and in applying two "silent" recalls (not happy I didn't get a notice), but the Security fault did not result in any action... I'm concerned it is a computer problem, expensive to repair. The problem may be that the Security fault isn't on all the time, so if I had a reader I could look when it is on.

The reality of that paragraph is first that Jerry contradicts himself in saying that the vehicle has a Security issue, but at one point says that its a base model with no electronic security. Not blaming him of anything here, but in a way that's a classic perception, and not an uncommon description that a customer might give to a shop. The security issue is likely real, plus it's intermittent. Tell me Mark are you trained and equipped to service that system? If so what scan tool are you using? (brand and software updated to 20XX model year)??

Sadly this is going to end up rhetorical, because I have to give the answer to make my point.

Real techs today, understand that the ONLY tool to service that system correctly is the GM tech II, and the shop has to have a subscription to SPS. What tool would you use if Jerry would happen to own a Ford with a similar reported problem? How about a Toyota; or a Mazda; a Honda, an Acura, a Lexus, a Nissan, an Infinity, a VW, a BMW, Mercedes, Kia, Hyundai? Or any one of the other manufacturers currently available in the US market? The reality is techs and shops need vehicle specific training, and specific O.E. tooling for each one of the manufacturers or else they are working with a handicap, and potentially will find themselves unable to actually complete a given repair without sending the car back to the dealer, or having a mobile diagnostic technician come to their shop, or in fact they could come to a shop like mine for about 90% of the most common vehicles on the road.

I ask you Mark are you genuinely equipped and trained to service the security system on Jerrys Truck? Would you be for all of the other manufactures that the readers here are likely to own?

By taking on that expense, uncommon in the industry, it impacts what a shop like mine has to charge for even the things that are indeed easy. You attempted to make that look as if it is dishonest with your response and I take extreme exception to that.

Dealerships, by their franchise agreement, have to be equipped for, and employ techs who are capable and trained to service things like Jerry's Security system. Only shops and techs who "get it" in the aftermarket step up to the plate and make the required investment in the tools, training and equipment required to do the complete job. Customers who understand this, realize that there are many ways to undercut the real professionals, but understand doing so causes either the professionals to charge even more for what they do, or else they have to dial back the services for which they are going to be able to perform for the customers. Or worse yet, simply shut down and no-longer be a viable option for the public.

Think that's an exaggeration? Look at how many dealers are being forcibly shut down. If your above average, your still not trained and equipped to fill the void caused by a dealer that closes. I can't do that simply because of the volume of work that could be displaced. (There are only so many hours in a day). Back yard Bob isn't going to do it, because he wont go to any updated schools, and he darn sure won't buy the tools.

Auto repair isn't cheap, it's actually under priced for what it really takes to do it correctly, and armed with the knowledge that is based in reality, a customer has a chance to find a real shop that will repair their car. That's my goal here Mark, exactly what was yours?

Hum, must be a combination of my typos and poor sentence structure.

I do understand, without any confusion, that my basic truck does not have any of the security features that the truck readout indicated was malfunctioning. That's part of the reason I suspect the computer, i.e., there is only one computer and it has options that may or may not be equipped, in my case the wireless key lock is not equipped (in fact my truck is so basic it has a key access only on the driver's side, none on the passenger side). That is also one of the reasons I was dissatisfied with the non-response by the service tech (who the dealer advertises are fully trained)to my complaint about the security fault display.

I was about ready to live with it as it should not (I guess) disqualify my vehicle at NJ inspection. But, related or not, the engine starter started to malfunction, not cranking the engine when the key is turned, but when the key is released to the "on" the starter cranks and the engine starts. I assume the security system has some function besides blowing the horn and flashing the lights (which doesn't happen), perhaps it also opens the starter circuit.

At what appears to be about $150 an hour at the dealer's shop I'm not in any hurry to take the truck back, as long as it continues to start.

Jerry said

I was about ready to live with it as it should not (I guess) disqualify my vehicle at NJ inspection. But, related or not, the engine starter started to malfunction, not cranking the engine when the key is turned, but when the key is released to the "on" the starter cranks and the engine starts. I assume the security system has some function besides blowing the horn and flashing the lights (which doesn't happen), perhaps it also opens the starter circuit.

Jerry, I think you are confusing the security system for a burgular alarm system. The security system is just an ignition interlock system or VATS system. No horn,head light,sirens or any other noise. The system just looks to see if the right key is being used. If not it wont't let the car start. If you still have your owners manual look at it and it should discribe the security light function.

Good Luck
With It

Bob

Thanks Bob, I did read the owners manual on both the SES and the Security (I'd have to, and can, go back to see exactly what the proper name is). The security Icon is a car with a padlock hocked through it, and it is red. The manual talks about how it is related to trying to enter and/or start the car/truck without using the electronic/wireless key. As I have a basic model, I do not have such a lock mechanism. I do recall the manual talking about the horn and lights going off and that that was both time-limited (a couple of minutes as I recall) and can be defeated by simply pressing the electronic key unlock button...which I do not have, either end. Again, that makes me believe my truck has a problem with the "computer" on board that somehow doesn't know the vehicle is not equipped with a wireless key access/lock.

That said, I have not had any problems with the false Security warning in the past three or four uses of the truck, including this morning in which I twice locked (manual setting from the inside) and unlocked, using a physical metal key. Maybe this has all passed :)

"That's my goal here Mark, exactly what was yours?"

I don't have a goal, I'm just describing the reality of the automotive diagnostic, service and repair business, not what's right or wrong.