How can I clear the engine service light - Page 2

mike sts · #16 (**permalink**) 04-24-07, 08:21 PM

My car is a 2005 blue sts leased in ohio I purchased at long caddilac in southboro MA, so far i have not found this dealer helpful they give me a hard time and seem put out with each of my request and are not helping me in the buyback process. The service manger told me he is not a lawyer but does not think my car qualifies because it is just a check engine light. I replied you cannot sell it or pass inspection with a check engine light it is a huge deal. The GM acted put out when i talked to him at first stating he has tried to comply with my 80,000 request then denied saying that, (my request was that they fill my gas tank before i picked up the car at the 4th repair attempt I have a 70 mile ride and a free oil change coupon) Terrible customer service at this point. If you hear of a tsb or any file number please let me know they state they are talking to a engineer at caddillac.

mike sts · #17 (**permalink**) 04-26-07, 10:13 PM

Hope this summary may help someone else with similar issue. got the car back again today 5th repair attempt last one before buy back. so far here is what has been done to fix this check engine light code caused by a too lean fuel mixture codes: po420 po171 and po174:
1 Recoonect hose and adjust air cleaner box
2 Replace fuel pump
3 Reset light to see if it would come back on
4 replace throtle body, clean fuel injection system
5 replace PCM, duct, maf, exhaust manifold, catalatic converter bank 1 sensor, oxygen sensor, fuel rail, intake manifolds, map sensor, o2 sensors.

So final diagnosis for this car was poor fuel injector flow and bad o2 ground. we will see if this fixes the problem. The best fuel mixture numbers they could get were bank2 10% bank1 7% 0 is the goal. Next step for me is to work a a settlement with caddi to pay for my time 15 hours, millage put on vehicle for road test and trips to the dealer (1000 miles), loss of use of the vehicle 3 weeks, pain suffering and aggravation. Iam thinking of a number in the thousands. Does anyone have any suggestions?

ewill3rd · #18 (**permalink**) 04-27-07, 07:45 AM

I forgot to close my case for you.
I'll try to get that done.
As much as I hate to say it at this point, I think you might see that light again.

The target fuel trims are actually 0%, but they should hang out below 10% normally. If they are over that then they are dancing closely to the threshold of setting the codes again.
The P0420 was a fixable problem and if they put a catalyst on then they fixed it. For a 420 it should be the right side cat. (bank 1)

Have they involved the local field engineer?
They didn't tell you what engineer they were talking to did they?
I always hate to hear about this problem and I haven't yet understood why some cars do this and some don't.

mike sts · #19 (**permalink**) 04-27-07, 08:57 PM

I was told they called the field engineer and they would talk on the phone but would not come out. They only have 2 for new england one in NY and one in ME. I was told they wont come until the car goes into buyback status. This does not make sense to me someone should have come out for this last attempt to fix. What number would cause the car to fail emissions for inspection? The service advisor told me these numbers are not close to failing the car but set the check engine light.

mike sts · #20 (**permalink**) 04-27-07, 08:59 PM

By the way they told me they parked a new car in the bay next to mine and swapped out part after part related to fuel delivery and emissions and could never get my car as low as their test car. How could this be? Is this a electrical problem or a mechanical design flaw?

ewill3rd · #21 (**permalink**) 04-28-07, 09:28 AM

I did the same thing, swapped parts off of a new car with the same result, no change.
I am not sure exactly what is happening and why some vehicles are more prone to do it than others. The real engineer that I talked to seemed to think it had to so with the air box, as I said, he sent me a special one and it did seem to help a great deal but the numbers were still not like I would like to see them.

A field engineer is usually very busy, and he just works with other production engineers to go after trouble children. I work with the one in this area a lot and he agreed with me that this seems to be a calibration issue. Even the air box they sent me was a "band-aid" and the car was bought back. The guy got a loaded up DTS and I guess he is happy. I think he really wanted the STS but couldn't take the light coming on. Plus it was worse for him because of the way he operates his car. (a lot of idling)

Based on what I know the real fix should be out in a month or two, I'll post if I hear any more about this from GM.

What makes the car fail emissions testing is not a "number" on the fuel trims. The trick is that a certain fuel trim number combination causes the code to set and turn on the MIL, when the MIL comes on any OBD emissions inspection will "fail". The presence of a current code will notify the emissions station computer and a failure will be registered.
There are two parameters on the data list that are monitored for each bank, long and short term fuel trim.
Without having to explain fuel trim in detail, basically the computer is watching the O2 sensors to see if the engine is running rich or lean.
If it is too lean the computer adds fuel and updates a fuel control table. These are called "blocks" and this all used to be called "block learn" and "integrator".
As the blocks are updated the computer adds or subtracts values to maintain stored fuel control for operating conditions. This is now expressed as "fuel trim".
Short term is a quick adjustment and will vary rapidly on the scan tool display. If short terms (ST) stay high (in your case, sometimes they go low) for a given time then a number is added to long term(LT). This is the new base. The ST numbers then usually fall back down and readjust, If ST numbers go high again, then LT numbers keep going higher.
Typically the computer will keep doing this until it sees specific levels at which it can keep ST at 0%.
If any combination of ST and LT equals 25, the computer will set a code for a set time period.
I think on STS they may have even lowered the limit to 18% recently.
The computer is actually compensating for the condition but EPA regulations state if the car is exceeding EPA standards by a certain amount the light has to come on and the code has to set.

Does any of that make sense?

mike sts · #22 (**permalink**) 04-28-07, 02:03 PM

Does everyone know of this fix? i asked my service manager about a upcoming fix he said it was BS, they asked the tac center and they were told of no upcoming fix? They could not find any information about the air box either

mike sts · #23 (**permalink**) 04-28-07, 02:06 PM

Does anyone know how many cars are effected?

ewill3rd · #24 (**permalink**) 04-28-07, 05:37 PM

I don't know how many cars are affected. I spoke to a GM software engineer for STS powertrain and he told me they were working on a calibration fix and it will be out, but it may be as late as beginning of production for '08.
TAC knows nothing, all they do is search a database of closed cases, those guys are paid to operate computers and most of them barely know which end of the car is the front.

If I could ever remember to dig out my TAC case folder I would close that case and they would have something else to go on. Once I submit it the information will go into their database and they will be able to tell you what I have already told you.
I am really bad about closing cases, which doesn't help other guys.

They had some cases where someone claimed a brake booster fixed it, I think one place claimed they replaced a leaking valve cover gasket, but I don't think that is the real issue here.
Have you seen the light come back on?

Onalaska · #25 (**permalink**) 04-28-07, 06:05 PM

I have a 2005 1SF. Was stuck in a traffic jam idling on and off for over two hours and never saw the SES light come on once so it doesn't happen to everyone. Also the cooling system on this car works, it never showed any signs of overheating. Two pusher fans plus an engine fan must take care of the heat.

mike sts · #26 (**permalink**) 04-29-07, 12:31 PM

It has been almost 200 miles and no light on yet

mike sts · #27 (**permalink**) 04-29-07, 12:33 PM

Quote:

Originally Posted by ewill3rd

I don't know how many cars are affected. I spoke to a GM software engineer for STS powertrain and he told me they were working on a calibration fix and it will be out, but it may be as late as beginning of production for '08.
TAC knows nothing, all they do is search a database of closed cases, those guys are paid to operate computers and most of them barely know which end of the car is the front.

If I could ever remember to dig out my TAC case folder I would close that case and they would have something else to go on. Once I submit it the information will go into their database and they will be able to tell you what I have already told you.
I am really bad about closing cases, which doesn't help other guys.

They had some cases where someone claimed a brake booster fixed it, I think one place claimed they replaced a leaking valve cover gasket, but I don't think that is the real issue here.
Have you seen the light come back on?

Who do they have to talk to to get the information that you have regarding a calibration update? Will this mean the car will always run a little lean?

mike sts · #28 (**permalink**) 05-01-07, 09:50 PM

well after 500 miles since the last fix the light is back on

ewill3rd · #29 (**permalink**) 05-02-07, 06:54 AM

mike,

I closed my TAC case on Monday. I am not sure how long it will take to get into their database.
If you want, I can send an email to the engineer I was talking to and ask him directly if he knows the progress of this issue.
I haven't heard from him for a while and my Service Director told me that GM has already taken this car back to look at it.
I am not sure where it went though.

mike sts · #30 (**permalink**) 05-02-07, 09:28 PM

Quote:

Originally Posted by ewill3rd

mike,

I closed my TAC case on Monday. I am not sure how long it will take to get into their database.
If you want, I can send an email to the engineer I was talking to and ask him directly if he knows the progress of this issue.
I haven't heard from him for a while and my Service Director told me that GM has already taken this car back to look at it.
I am not sure where it went though.

Thanks that may help you know much more about this issue than anyone at long caddi, they want one more chance to work on my car they are sending the field engineer to work on it next thursday, i have told them i am looking for them to trade a 2006 sts for my 2005 with the hope the 2006 has worked out some of these bugs