p0300 2006 Cadillac DTS
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Cadillac DTS Forum - 2006 through 2012 Discussion, p0300 2006 Cadillac DTS in Past Cadillac Vehicle Discussion; hey guys need help, ive been a professional mechanic for over 20 years and am having trouble figuring out p0 ...
  1. #1
    bjm6887 is offline Cadillac Owners Member
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    p0300 2006 Cadillac DTS

    hey guys need help, ive been a professional mechanic for over 20 years and am having trouble figuring out p0 300 on my 06 dts performance. tested usual suspects, fuel pressure. replaced plugs, cleaned fuel injectors, checked for air leaks. no lean or rich codes. the misfire occurs mainly at idle. tried unplugging maf, map. no help. replaced 2 coils for giggles (3,5), ran better for awhile then came back. sure feels like electrical problem, runs good then like switch will chuggle on/off. I think I might have bad ecm. any ideas? thanks for any help

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  3. #2
    Superjim's Avatar
    Superjim is offline Cadillac Owners Connoisseur
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    Re: p0300 2006 Cadillac DTS

    Do you have access to a TECH 2 ??
    It will show exactly which cylinder is misfiring and will probably ALSO show what is causing it.

  4. #3
    danog is offline Cadillac Owners Fanatic
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    Re: p0300 2006 Cadillac DTS

    What type of scanner are you using. You may not be able to see advance GM codes. P0301.through P0308 for each cylinder. If you don’t have a TECH 2 You could use a infrared thermometer and check the temp at the Exhaust Manifold of each cylinder. The one with the coldest temp is the misfire.
    A bad plenum duct will act like a misfire and it may not give codes p0171 p0174. Was there any oil on the plugs. How many miles on the car. Are you using TOP TIER Detergent Gasoline.

  5. #4
    bjm6887 is offline Cadillac Owners Member
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    Re: p0300 2006 Cadillac DTS

    no access to tech 2 but used used snap on scanner to test individual cylinders and the miss just jumped all around, replaced the 2 coils on the cylinders that were acting up the most at that time and the hardest to change 3&5, got better but still have random misfire at idle in gear. seems to come and go. thinking about replacing all coils but didn't want to waste money if I had bad ground or ecu. etc ..

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    some oil on coil boots but not horrible, sprayed carb cleaner on plenum duct, and intake manifold. and looked at plenum, nothing obvious or rpm change with spray, if I had vacuum leak I should see lean conditions but I haven't... 100k miles weird

  6. #5
    MoistCabbage's Avatar
    MoistCabbage is online now Cadillac Owners 10000+ Posts
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    How many miles on the car?

    When was the TB last cleaned?

  7. #6
    bjm6887 is offline Cadillac Owners Member
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    Re: p0300 2006 Cadillac DTS

    100k miles. just cleaned throttle body and injectors with bg products

  8. #7
    danog is offline Cadillac Owners Fanatic
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    Re: p0300 2006 Cadillac DTS

    I would replace the last two on the back 1 and 7 that way you get rid of apposing cylinders Screwing the the readings with the scanner.
    You can take out the front bolts in the sub frame that way it will give 3 or 4 more inches at the back , don’t remove the dog bones.

  9. #8
    bjm6887 is offline Cadillac Owners Member
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    Re: p0300 2006 Cadillac DTS

    anyone hear of bad ecm, grounds on dts?

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    might try that danog, didn't have to roll motor or anything just took off air valve and coils come right out

  10. #9
    danog is offline Cadillac Owners Fanatic
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    Re: p0300 2006 Cadillac DTS

    The 06 /09 have been rock solid its ether go or no go, no ground problems. !0/11 thats a bunch of other problems.

  11. #10
    grullon10's Avatar
    grullon10 is offline Cadillac Owners Fanatic
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    I hope what is happening to you is not what happen to me I was having the same issued when the car was illing it was the timing. My car at 100,000 miles one day I remote star the car. After couple of minute the car went off I was walking to I could see it but hear it . The junp the timming one deagree . The plastic on the timing guide were eating up by the timming chain that why I was having p0300. It was the even # . Goodlk.

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    If I miss write something is because I'm doing it from my phone " I could see the car but not hear it"

  12. #11
    phigment is offline Cadillac Owners Fanatic
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    Re: p0300 2006 Cadillac DTS

    Following this thread with interest. My 06 has 130k miles now. Starting around two weeks ago it would chug while in drive, at idle, with the brake applied(stop light). Its like two or more cylinders stopped getting gas for a split second. The car would cough for a second and then return to normal idle. Fuel pressure is good. Replaced all plugs and they all looked pretty good for 130k miles. No codes at all. All injectors have been checked and show good. Car is not running lean. Now my intake bolts were loose and I did tighten them awhile back. I need to get a can of carb cleaner and have at it while watching fuel trim. Is it possible that a slight intake leak could cause this? Its not consistent and that seems to make diagnosing it harder.

  13. #12
    bjm6887 is offline Cadillac Owners Member
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    Re: p0300 2006 Cadillac DTS

    grullon, I don't think it's timing problem. engine quiet, clean oil , misfire comes and goes. if timing was off it would run bad all the time, runs fine for days then acts up, seems electrical ran fine in Iowa runs erratic in Colorado, maybe map sens bad but no codes

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    phigment I think we're chasing the same problem, read about injector problems but I flushed them and no lean codes, I get p0420 now and then but think that's a software update issue

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    also when I was watching misfire monitor it would glitch on both banks, then none etc..

  14. #13
    phigment is offline Cadillac Owners Fanatic
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    Re: p0300 2006 Cadillac DTS

    Funny you mention p0420. I was getting that a few weeks back. That is when I found my loose intake bolts. I reset the code after tightening the bolts and it has not returned. It might be worth mentioning that I was not experiencing this current problem when I first got the p0420 code. Also, there is a software update(thanks forum) to resolve the false positive p0420. I had that done when I had the injectors checked.

  15. #14
    danog is offline Cadillac Owners Fanatic
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    Re: p0300 2006 Cadillac DTS

    The EGR could cause the problem. If the EGR valve pintle that is not seating properly when it is in the closed position. I have made a plate to close of the ports while I drive the car to see if the condition go’s away. Leave the EGR connected . The pintle is spring loaded. Try pushing the pintle in and see if it returns with out sticking.

    Check for circuit number 3110 being shorted to ground at the EGR valve heat shield.

    Are the oxygen sensors readings ok good swing? How is the long term fuel trim

  16. #15
    bjm6887 is offline Cadillac Owners Member
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    Re: p0300 2006 Cadillac DTS

    I'll keep in touch! driving me nuts

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    danog, when I last checked all my readings were good, will check egr possibilities, thanks for the tip

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