CHECK ENGINE LIGHT ON AND OFF ON 2005 BUICK ALLURE / LACROSSE

karounio

I purchased a loaded 2005 Allure / Lacrosse with 85K kms, now 88K. Ever since out of the blue the check engine light (never with any codes or message accompanying), will come on suddenly after being OK for a few hundred miles?? This car is so spotlessly in good shape, even the engine shines my mechanics can't believe the new condition and low mileage BUT as of the last time it came on (the third time), I have replaced the steering pressure hoses, return line, purge solenoid. ALSO, I have the trouble I have read about on-line with the console lights suddenly going dim and coincidentally, it did so just prior to check engine light on 'this' time. I also have the passenger side seat airbag light on steady - won't go off, although was off for a time when purchased. This car has been checked tip to tail and they say every part looks like new to the extent that my mechanics are shaking their heads too. I DO NOT FEEL SAFE driving with the check engine light popping on out of nowhere, even though I know my mechanics have gone over the car with a fine tooth comb trying to assure me it is just a glitch. Just a glitch? How can I fix it? One last thing: Does everyone's Lacrosse make ping noises when shut off after a drive as though it is extremely hot? I 've never heard this before and am told it is due to the manifold so close to the top of the engine so I can hear it where I could not so well with my LeSabre. Please, please...can anyone help with guidance....please? I Three of us ran the car through Carfax and another system, prior to purchase with no issues returned. Help.

ray80

Console lights dimmed before CE light this time, do you know if they did or did not the other times? Perhaps you missed it. I might not be surprised if the CE was due to same issue as console lights (whatever it is). I might wonder about intermittent issue with alternator that causes low voltage and messes with stuff before self- correcting, but it could be other things like bad ground, bad battery cable or something entirely different .

imidazol97

There has to be a code for the check engine light to be on. Has it been checked by a GM dealer WHILE the light is on? Even if the light is not on, there should be a history showing a code for which the light was on.

If you've been having it checked by local garages, I'd suggest taking it to a dealer with a good reputation in your area while the light is on. Explain that you want to be able to bring it in to see what the light means. I suggest a dealer because the scanners at some garages aren't full coverage. Even my Malibu had an odd code in history while it was new that seemed to be from the OnStar system operation.

The only thing I find curious is the what you call pinging. It might be coming from the catalytic converter under the car as the pipe in that area cools after running hotter than normal. There are oxygen sensors in front of and after the catalytic converter to turn on the CEL but those both would show codes if they turned light on due to converter being overwhelmed by excess fuel or being ineffective.

Mr_Shiftright

imidazol97 said:

There has to be a code for the check engine light to be on. Has it been checked by a GM dealer WHILE the light is on? Even if the light is not on, there should be a history showing a code for which the light was on.

If you've been having it checked by local garages, I'd suggest taking it to a dealer with a good reputation in your area while the light is on. Explain that you want to be able to bring it in to see what the light means. I suggest a dealer because the scanners at some garages aren't full coverage. Even my Malibu had an odd code in history while it was new that seemed to be from the OnStar system operation.

The only thing I find curious is the what you call pinging. It might be coming from the catalytic converter under the car as the pipe in that area cools after running hotter than normal. There are oxygen sensors in front of and after the catalytic converter to turn on the CEL but those both would show codes if they turned light on due to converter being overwhelmed by excess fuel or being ineffective.

I'd have to agree--it's possible your local garage is in over their heads on this one. This problem may not be super simple to solve but it is solvable. I'd also tend to agree that the battery cables, battery ground and alternator output should be checked carefully. You know, even if you bought a cheap code reader for $15, it might be handy to plug it in while that CEL is on.

thecardoc3

imidazol97 said:

There has to be a code for the check engine light to be on. Has it been checked by a GM dealer WHILE the light is on? Even if the light is not on, there should be a history showing a code for which the light was on.

There is a possibility where this could occur. The instrument cluster is responsible for turning the light on under the following conditions:
Bulb Check at start-up.
If the PCM has set a code and commanded the lamp on which is done via two way communication.
If the Instrument cluster has lost communication with the PCM.

The lamp could be turned on incorrectly if the instrument cluster itself has a problem. Scan data would show the PCM as commanding the lamp off and the instrument cluster data would concur that the lamp should be off. If the lamp is on when everything else shows it should be off, a tech with a fully capable scan tool could go into the bi-directional controls for the instrument cluster and try to directly command the lamp on and off. If the lamp doesn't follow those commands then it most likely is a failure of the lamp driver in the instrument cluster.

This is one of those times where a tech has to see and analyze the failure while it is happening in order to prove it.
There are some other potential causes, but they get to be very unlikely based on the reported condition.

imidazol97

Glad to see others expand on the CEL. My 03 leSabre with 150Kmiles had the check engine light flash on occasionally but set no code. It did not stay on--it flashed as if it were sensing misfiring and then it was gone. Eventually it did set a code for misfire on one cylinder.

For the Poster's console lights, I am suspicious this may be the problem on some cars where the auto on/off lights are turning the headlamps on/off and the interior lights, the dash lights, change when that happens. I suspect the Allure is one of the cars with the console lights on during the daytime for background lighting to make the gauge visible. Then when the headlights come on, the background lighting falls in intensity because the surroundings would be darker at dusk/dawn. I know the light sensors on our more recent GM cars, 08 and 14 (and 15) will sense the sunlight as dusk/dawn when it's heavily clouded or the light is at an oblique angle to the sensor because the sun is low int he sky. This fools the sensor and the lamps change from daytime with bright background on the console items to the night time settings. My 08 Cobalt is especially bad at that.

The test that the Poster can use is turn the brightness control on the dash to adjust the brightness of the backgorund console lights at night when the console lights dim on their own. If the brightness control turned all the way up will bright back the console brightness to visible then your headlamps system is on night setting and it's not sensing that the sun is up and bright enough for daytime.

A second test to see if the headlight system has gone to night settings is to see if the headlamp switch will turn the headlamps on bright, shown by the indicator on the speedometer area. During daytime headlamp settings the bright lights can not be turned on permanently (they still can be turned on using the flash-to-pass switch by pulling the turn signal lever up).

imidazol97

To support my suggesting having a good tech at a GM garage analyze the CEL, my 14 Malibu did not do the stop/start engine pause at times when the listed parameters said it should after part of a year of driving. The dealer found there was a code in history indicating a turnoff signal from OnStar, which I took to mean that OnStar had sent a signal to slow down the engine operation such as when OnStar is authorized by police to shutdown the vehicle that has been stolen, e.g., while it's driving.

thecardoc3

imidazol97 said:

Glad to see others expand on the CEL. My 03 leSabre with 150Kmiles had the check engine light flash on occasionally but set no code. It did not stay on--it flashed as if it were sensing misfiring and then it was gone. Eventually it did set a code for misfire on one cylinder.

Good one. That's exactly how the system is supposed to work, which however can be a bit of a nightmare for techs. It works like this:

The light must come on if the vehicle might be polluting the air in excess of the allowable FTP (federal testing procedure) by a given margin usually reported to be 1.5 times the limit. When the PCM detects a misfire, it must first classify if it is just one that can impact the vehicle emissions which would be a calculated percentage of events over 1000 crankshaft revolutions or if it is a catalyst damaging one which is calculated as a percentage over 200 crankshaft revolutions. It's important to note that the catalyst damaging misfire also has an engine load aspect to it. The greater the engine load, the more likely the misfire would be able to damage the catalyst.

Now armed with that baseline, the system detects a misfire and responds by shutting off the injector for that cylinder. With no fuel going into the cylinder that was detected to be misfiring the question to be asked is, will it raise the vehicle emissions above the FTP limits and/or will it damage the catalyst? If the answer based on the failure management mode that the PCM enters is no, then the system DOES NOT have to code and set a mil. Then when operating conditions change from the detected misfire the computer will turn the injector back on and evaluate if the misfire is still present or not. If it isn't then normal operation resumes and beyond historical misfire counts which could be found in some manufacturers live data stream and now required in Mode$06 the event ends.

This can be quite a challenge for a anyone to sort through. A lot of the time basic maintenance such as "tune-up" components may be advisable based on mileage or specific vehicle knowledge but without proving correlation to the flashing mil by direct verification and testing there is no way to know if the service will have any impact at all on the symptom(s). From the consumer side this is usually viewed based on the results of a given individual outcome and sometimes that will be: "They tuned it up (or whatever) and the problem went away" And of course it could be "They tuned it up (or whatever) and it's still doing the same thing". Now put that into context with all of the anecdotal reports that you have ever seen and it reveals why many of them were as difficult as they turned out to be. There is also the rest of the dynamic in play when the failure cannot be duplicated and verified. Before the decision is made to try to fix it, the situation started with the choice of do something versus do nothing which can be recognized as occurring by the OP's description. Both the do something and the do nothing approaches are simultaneously anecdotally both correct and incorrect. Repairing a vehicle problem shouldn't result in a paradoxical challenge, but the more you understand just what all of the outside influences really do to the process the more obvious it becomes as to what they really accomplish.