Rich Posted February 5, 2015 Report Share Posted February 5, 2015 I drove the 1997 Eldorado this morning and noticed the amber Service Engine Soon indicator was illuminated. I shut down, removed and replaced the gas cap and restarted. The indicator remained lit. I ran the codes and found a half dozen which my car seems to have a preference for. I've seen these all before and I just checked them on the OBD II code list, they are all History codes: PCM P0300 H PCM P0603 H PZM B0533 H PZM B1552 H PZM B1558 H MMM B2144 H Since they're all History codes, I understand they will clear themselves at some point. I've seen these all before, maybe multiple times throughout the years so I assume they aren't critical. The car seems to be running great. What I'm wondering is whether the Check Engine Soon indicator will reset itself or do I need to reset it manually? I really hate staring at that indicator while I'm driving. Based on the codes set, would there be any issue in resetting the Check Engine Soon indicator, and if not, how do I reset it? Link to comment Share on other sites More sharing options...
winterset Posted February 5, 2015 Report Share Posted February 5, 2015 It would reset itself after a few engine cycles start/reach operating temperature/stop/cold start. BUT that is if the condition does not re-occur. I think resetting is a good idea to get an understanding of how often the problem is happening. Over the years on this forum, i think we learned that a misfire on a cold start can mean something serious. Are you loosing coolant? There can be coolant seeping into a cylinder thru the head gasket. I don't mean to scare you, but you should address the misfire problem. Do you have any other symptoms? Also, consider cleaning your battery terminals. Link to comment Share on other sites More sharing options...
Rich Posted February 5, 2015 Author Report Share Posted February 5, 2015 I'm the original owner of this car and have it serviced as per the owner's manual, perhaps even a bit better than recommended. I'm not loosing coolant. The head gaskets failed seven years ago and I had them done at my local Cadillac dealer then. I made sure they did all 20 headbolts and was charged appropriately. They assured me then that when they did the repair they did it absolutely according to Cadillac specs and procedures. My battery was just replaced this past November, also by a local Cadillac dealer. I also had the cooling system serviced that day, the second cooling system service since having the headgaskets done in February 2008. No other symptoms. The car runs like a champ! You said that the indicator would reset so long as the condition does not re-occur. Based on the codes set, and the fact that they are all History and not Current, wouldn't the expectation be that the condition was temporary, or no longer occurring? Link to comment Share on other sites More sharing options...
Cadillac Jim Posted February 5, 2015 Report Share Posted February 5, 2015 The one that turned on the MIL is the P0300. The car has a miss that is bad enough to affect emissions and possibly cat life. If the usual tune-up process doesn't clear it, you should look at the plug wires to start. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
KHE Posted February 5, 2015 Report Share Posted February 5, 2015 Clear the PCM history codes and the light will go out. Enter diagnostics and when PCM? is displayed, push the fan up button. When PCM CODES is displayed, push the fan down button. CLEAR PCM CODES will then be displayed. Press the fan up button and then exit the diagnostics either by pressing the auto button or turn off the ignition switch. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Rich Posted February 5, 2015 Author Report Share Posted February 5, 2015 I will try to clear the codes tomorrow then. Hopefully, this will cause the Service Engine Soon light to go out. Hopefully, I won't experience this again, but I'll keep the tune up in mind. I never thought a tune up was needed as the car starts right up every time on the first crank, always runs strong and smooth. Even on hard acceleration, the acceleration is very linear all the way up to redline. It doesn't "break up" at higher RPM's and there is absolutely no indication that anything is amiss. Thanks for your help guys. I'll be keeping an eye on this. Link to comment Share on other sites More sharing options...
KHE Posted February 6, 2015 Report Share Posted February 6, 2015 There is really nothing to tune up on these cars other than replace the spark plugs if they have over 100,000 on them. The wires are tested very easily by looking for arcing when the engine is running - hood up, dark outside. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
winterset Posted February 6, 2015 Report Share Posted February 6, 2015 You'll have to try to understand when the misfire happens. Could be when the car is cold, it misfires, then after it warms up, the misfire goes away, so it's history. You might also want to check under the hood at night, and look for blue arcs from the wires. When were the plugs changed? Link to comment Share on other sites More sharing options...
Rich Posted February 6, 2015 Author Report Share Posted February 6, 2015 The Eldorado has 135,000 miles on it. The plugs and wires were changed about eleven years and 70,000 miles ago. I think one coil pack was changed out at that time too. I think I'll look for the blue arcing one of these nights but maybe I should consider plugs and wires if I can't get rid of the error codes and MIL. Link to comment Share on other sites More sharing options...
KHE Posted February 6, 2015 Report Share Posted February 6, 2015 If there is not any arcing, changing the plug wires would be a waste of time and money. A blue glow around the wires is normal. It is possible one or more of the plugs has shed the platinum pad on the ground electrode but if that happens, you will notice the misfire. I'd clear the codes and see if any re-set. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Rich Posted February 6, 2015 Author Report Share Posted February 6, 2015 I just cleared the codes as per the above instructions and the MIL went out as expected. Did a bit of driving getting the car up to operating temperature. Redlined it a few times while out. Had four of five subsequent shutdowns and start ups during that time, all but one of which were starts with the car at full operating temperature. No issues yet, no MIL. I can't stress how well the Eldorado is running. Strong and smooth as ever. We'll see how this goes. Again, thanks to all for your expertise. Link to comment Share on other sites More sharing options...
Jimbe Posted August 31, 2015 Report Share Posted August 31, 2015 Oh my gosh, I had same issue ,cleared PCM history and light went away!! I get hyper when a light comes on.Just got 99 deville and really like it.Thanks Bucket Link to comment Share on other sites More sharing options...
Cadillac Jim Posted September 1, 2015 Report Share Posted September 1, 2015 The MIL light always goes out when you clear the codes (unless the problem is always present and CURRENT). It doesn't mean that the problem is gone. Wait and see if it comes back. If it does, THEN you need to diagnose and fix the problem. You can start by writing down the OBD codes and posting them here, as Rich did. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
barczy01 Posted September 3, 2015 Report Share Posted September 3, 2015 Check your battery connection and the coil towers on the coil pack. They get rusty. Link to comment Share on other sites More sharing options...
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