Jeff Posted November 5, 2004 Report Share Posted November 5, 2004 Hello again- It's been a while... Whenever I sit at an idle for a while- like when I'm at my speedy Credit Union's drive through teller - or at the Whataburger window - my "service engine soon" light comes on. After about 3-4 more trips (crank, drive, kill it) it goes off. I thought it may go off after a certain distance but it doesn't. I'va had it come on, and I drove over 200 miles non stop with it on, and it still took 3 more trips (crank, drive, kill it) to get it to go off. There are no codes- just the light. Any ideas? Jeff Link to comment Share on other sites More sharing options...
taxman Posted November 5, 2004 Report Share Posted November 5, 2004 My buddy had this same type of problem & symptoms with his '96 STS. It was the crank position sensor. He wasn't getting any codes either. Replaced at dealership and the problem went away. Good luck!! Link to comment Share on other sites More sharing options...
PAUL T Posted November 5, 2004 Report Share Posted November 5, 2004 Correct me if I am wrong but, if the "service engine soon" light comes on there is a code. Depending on when you check the diagnostics, if the light is on there should be a "current" code, if it was on then goes off there should be a "history" code. Sounds like an intermittent problem and there really should be a code. Does the car run differently with the light on? Link to comment Share on other sites More sharing options...
Poobah Posted November 5, 2004 Report Share Posted November 5, 2004 The way I understand it (and the way my '94 works), the "service engine soon" light simply alerts the driver to the fact that a code has been set. When the problem occurs, the code is set and held as "current" until the ignition is turned off. If the problem is not ongoing, the code will be kept as "history" for the next (if I remember correctly) 60 ignition on/off cycles, unless the code is manually cleared in the mean time. A code in history does not turn on the "service engine soon" light. If you are getting a "service engine soon" light and no codes, I would suspect a problem in your diagnostic system somewhere. Happiness is owning a Cadillac with no codes. Link to comment Share on other sites More sharing options...
nitrous1 Posted November 5, 2004 Report Share Posted November 5, 2004 My 96 STS does this too - it sets codes P171 and P174 if I let it idle too long. Link to comment Share on other sites More sharing options...
Jeff Posted November 7, 2004 Author Report Share Posted November 7, 2004 Sorry for the delay- Every time I check the codes, they are all history codes- never current. ?? No it does not run differently when the light is on- just the light. ?? I'll check to see which codes it says are "history" in the meantime... Jeff Link to comment Share on other sites More sharing options...
Poobah Posted November 7, 2004 Report Share Posted November 7, 2004 In order to get a "current" code, you would have to pull the codes after the "check engine soon" light comes on and before you turn off the ignition. (It is possible that an intermittant problem will set a code then move it to history before the key is turned off, I'm just not sure about this.) I would suggest you pull all your codes, write them down for the record, then clear them. A lot of Cadillacs carry meaningless or redundant codes in their history. For example, disconnecting your battery will set two or three codes. Once the slate has been wiped clean, I would just let the car idle in the driveway for a while and, with any luck, you'll get the "service engine soon" light. Shut the engine off and pull the codes. Whatever you get will be the source of your trouble. Good luck! Happiness is owning a Cadillac with no codes. Link to comment Share on other sites More sharing options...
PAUL T Posted November 7, 2004 Report Share Posted November 7, 2004 My 96 STS does this too - it sets codes P171 and P174 if I let it idle too long. P171 - fuel trim system lean bank 1 P174 - fuel trim system lean bank 2 Link to comment Share on other sites More sharing options...
nitrous1 Posted November 8, 2004 Report Share Posted November 8, 2004 My 96 STS does this too - it sets codes P171 and P174 if I let it idle too long. P171 - fuel trim system lean bank 1 P174 - fuel trim system lean bank 2 Paul, Thanks for the information. I knew what the codes represented thanks to my FSM, but so far I haven't had much luck in finding the cause of the problem. I believe that I have a vacuum leak on the back edge of my intake manifold (I did the old carb spray trick), but I haven't had time to pull the intake off and reseal it. The car was running fine before I took in for the fuel rail recall, I guess the dealership jostled something that the shouldn't have. Thanks, Dan Link to comment Share on other sites More sharing options...
Poobah Posted November 8, 2004 Report Share Posted November 8, 2004 If it's something the dealer did, they should make good on it! Happiness is owning a Cadillac with no codes. Link to comment Share on other sites More sharing options...
nitrous1 Posted November 8, 2004 Report Share Posted November 8, 2004 If it's something the dealer did, they should make good on it! I can't prove that the dealership did anything. I didn't drive the car very much for nearly a month after I had the fuel rail recall done. The SES light came on while I was stopped at a traffic light one morning, about a month after I had the car at the dealership. They could have bumped something, or maybe it was just time for something else to malfunction. I can't say for sure either way. I really don;t want to take the car back to dealership because I have some issues with the quality of work I received while it was there. I'd rather just fix it myself and forget about it. Link to comment Share on other sites More sharing options...
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