"service engine soon" light

robert graham

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My 1996 Buick Roadmaster with LT-1 350 V8 with 190,000 miles has a "service engine soon" light that comes on for a day or so and then goes off for a day then back on....no apparent problems with the running of the engine....my mechanic has put the engine on his code reader and can't seem to nail it down...wants me to leave the car with him for a few days to "run a few tests with the engine overnight cold"......mentioned a faulty fuel pump or some other problem?....any of you automotive wizards have any ideas of what this may be?....wonder how many different faults can turn turn this light on? I know a small piece of black electrical tape over the light is the simplest/easiest fix but I really need to know what this is?.....Any ideas?....
 

alldodge

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There is all kinds of things which can turn the light on. Anyone of the faults being set needs to be gone for 3 cycles to clear. My initial thought is either an O2 sensor or expansion tank tied to a loose gas cap. Had one on the wife's Montero which was the O2 sensor past the Catalytic converter which stayed on. Replaced the sensor and it didn't go out. Car ran fine, no change in mileage, so we ran it for another 80K without issue. The light gave a nice glow in the evening :rolleyes:

Just wait for it to stay on
 

GA_Boater

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Service engine soon usually means it's time for a mileage related servicing. Like oil change, plugs, etc. Normal maintenance items. If you still have the manual see if there is any scheduled maintenance item(s) around 190K miles.

This is a good description of the "service engine soon" light.;

Service Engine Soon Light ? What is Wrong?
Before you can determine what needs done, you must first understand what the service engine soon light means and how it is triggered. The service engine soon light is often confused with the check engine light. The check engine light is a light to alert you to a possible problem with the exhaust and emissions systems. This will let you know when there is an excessive concentration of carbon monoxide being emitted through your exhaust system. The service engine soon light can cover many issues, from minor to major. Once you have determined that it is the service engine light that is illuminated and not the check engine light, you will have to perform an inspection to determine where the problem is located. In some vehicles it simply means that it is time for an oil change. Your car?s computer can keep track of engine rpm, temperature, and miles driven to give an idea on when the oil life has ran out. The light can also tell you if the fuel to air ratio is not correct. You will want to look in the owner?s manual or service manual to see what the light is telling you. It is always a good idea to check with your local mechanic or auto parts store to look for problems for you.
How Soon Should You Respond to a Service Engine Soon Light?
Your service engine light should not be considered a panic button. Just because the light says ?soon? does not necessarily mean that you will need to make a repair soon. It would be wise to have a thorough inspection done to determine if you have any serious problems. One thing you can do as soon as possible is to perform fluid checks. Make sure that you have enough engine oil, windshield wiper fluid, transmission, and brake fluids. Top off any levels that are low and check for any leaks or signs of wear or damage. The severity of the problems found during the inspection would determine the urgency of the repairs that are needed. Any leaks and clogs should be remedied as soon as possible, as these issues can severely affect the safety of the car. For instance, a leak in the brake line could cause the brakes to fail, resulting in an accident. If your car has a leak somewhere, you should not drive it until you get it fixed.
A sort of related issue - http://www.cartalk.com/content/i-have-disturbing-problem-i-own-buick-roadmaster
 

thumpar

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We had an issue where the code was not being stored in the computer. The mechanic has a little device they plugged into the diagnostic port and told us to come back when it has happened. It just reads all the data and records it for later use. They hook it up via USB to the computer and is gave the code. Maybe see if your mechanic has anything like that.
 

tpenfield

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190,000 miles and the thing says to "check engine soon" . . . wow . . . I would think so. :D

I'd go for the black tape idea, so long as you are up to date with normal servicing.

BTW - my "check engine light" came on, so I pulled over, stopped the car, opened the hood and checked the engine . . . the light didn't go off :noidea:
 

robert graham

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I carefully do all the service on my engine, fresh oil, topped off fluids, clean spark plugs, etc.....a few minutes ago I lightly hosed off the engine just to keep the dust off....and the light went out! I'm beginning to think this may be some issue with the emission control systems, O2 sensors, etc....Best I can do is drive it a few days until the light comes back on and leave it with my mechanic to try and identify the problem....It is a very sweet running Buick, but 18 years and 190,000 miles....maybe time for a Yukon or Tahoe for hauling the boat?....I always get attached to my cars and boats and tend to run them forever or past their prime.....sorta like me!....
 

robert graham

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We had an issue where the code was not being stored in the computer. The mechanic has a little device they plugged into the diagnostic port and told us to come back when it has happened. It just reads all the data and records it for later use. They hook it up via USB to the computer and is gave the code. Maybe see if your mechanic has anything like that.


That's a handy tool....a code storage device....I'll ask him about it!....
 

redneck joe

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hate to say it but there are times when a dealer service center is the best option.
 

gm280

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With that high a mileage, it could easily see a cracked vacuum hose causing such erratic "check engine" lights going on and off. I had a vacuum canister hose and valve cause such a situation once and I fixed it myself with a new vacuum line and a valve. But there are so many codes that cause a check engine light to go on that the issues can be near limitless. A standard OBDII reader recorder would help locate the problem. The fact that it comes and goes could even be a gas cap seal leaking. FYI, OBDII codes were mandatory since 1996 for every car sold in America. And every car/vehicle sold has to use the same codes for the same type problems in every vehicle as well. So all vacuum codes are the same reading for vacuum issues. And equally so, all O2 sensors have to use the same code reading as well, and so on regardless what manufacture it is. There are segments of code that can be unique for each vehicle, but the normal codes has to be the same for every car. And ever OBDII output plug also has to be located under the drivers side steering section as well. Those were laws issued by the Federal government. At least that was true up to a few years ago. I don't know if those rules still apply for the newer vehicles now or not... I don't own anything that new!
 

Tim Frank

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Deleted info not supported by facts.
There's not much left after that.... :facepalm:
 
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bigdee

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1996 and 190,000 miles? Count your blessings that is not on full time!
 

thumpar

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Our burb has 380k+ on it. Mileage doesn't scare me. It is lack of maintenance that kills stuff.
 

Tim Frank

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Tim, "Service Engine Soon" = "Check Engine". That's just a GM thing.

Wonder where GA_B got his info in post 3?
My Subaru has both "check engine' AND "Service required" lights.

.
 
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bruceb58

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Wonder where GA_B got his info in post 3?
My Subaru has both "check engine' AND "Service required" lights.

.

Gm vehicles have just the one.

Not where GA_B got his info but it's not for a GM vehicle. Even states it's ODB-II related in my Silverado owners manual.
 
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GA_Boater

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Wonder where GA_B got his info in post 3?
My Subaru has both "check engine' AND "Service required" lights.

.

I just Googled "what does a service engine soon light mean" and picked what I took to be the clearest explanation out of the 2.2 million hits. I looked at each and every one :rolleyes:

http://danddautoworks.biz/2013/why-t...might-come-on/

The C&P I did is generic, not vehicle specific.

Over the years, I have had both lights. If you take a car in for emission testing with a "check engine" light, the car will fail. I've had them fail with no check engine light, OBD I. The "service soon" means nothing for emissions.

My opinion - the "service engine soon" should should be changed to "As a vehicle manufacturer and you being a lazy consumer not following recommended maintenance intervals, take this vehicle to the nearest XXXXXX dealer to turn the light off in exchange for a buncha money." LOL

EDIT - There are several TSBs related to 1996 Buicks and "Service Engine Soon" light.
 

robert graham

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I know how to turn the light off....just disconnect the battery for a few minutes....but it doesn't address the cause of the light being on....
 

bruceb58

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I know how to turn the light off....just disconnect the battery for a few minutes....but it doesn't address the cause of the light being on....
If the light goes out by disconnecting the battery, there is a code being set and your mechanic's code reader is not reading which code is being set.

Has your mechanic had his code reader connected while the light is set?
 

garbageguy

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I carefully do all the service on my engine, fresh oil, topped off fluids, clean spark plugs, etc.....a few minutes ago I lightly hosed off the engine just to keep the dust off....and the light went out! I'm beginning to think this may be some issue with the emission control systems, O2 sensors, etc....Best I can do is drive it a few days until the light comes back on and leave it with my mechanic to try and identify the problem....It is a very sweet running Buick, but 18 years and 190,000 miles....maybe time for a Yukon or Tahoe for hauling the boat?....I always get attached to my cars and boats and tend to run them forever or past their prime.....sorta like me!....



I do the same. My 2003 Grand Prix, 3.8 l, with 198k had a similar deal. Went to my trusted mechanic who checked/cleared code(s), told me to try getting a new fuel filler cap asap. I did that immediately, and the light has been off since.
 
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