03 STS rough IDLE P0300 & U1016 Code
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Results 1 to 9 of 9
Northstar Engines and System Technical Discussion Discussion, 03 STS rough IDLE P0300 & U1016 Code in Cadillac Engine Technical Discussion; Hey guys, I need some help. I've got an 03 Seville STS with 70k miles on it and it just ...
  1. #1
    ktraub is offline Cadillac Owners Member
    Automobile(s): '03 STS w/Nav, '93 SLS
    Join Date
    May 2005
    Location
    So, MD
    Posts
    59

    03 STS rough IDLE P0300 & U1016 Code

    Hey guys, I need some help. I've got an 03 Seville STS with 70k miles on it and it just started idling rough when warm with the A/C on. With A/C off, it still idles a little rough, but not as bad. Also, it seems to sputter a bit when under WOT and if at WOT for more than 5 seconds, the Service Engine Soon light flickers and sometimes stays on. When I dump the codes, I get a History P0300 and occasionally I see a History U1016.
    I've looked up the P0300 (multi-cylinder misfire) and the U1016 (lost communication with PCM).
    I'm a little low on $$ right now due to family problems so I'd appreciate some advice on the least expensive way to approach the repairs.
    Any help would be appreciated.

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    mikeay's Avatar
    mikeay is offline Cadillac Owners Fanatic
    Automobile(s): 1996 Cadillac Seville STS
    Join Date
    Jul 2005
    Location
    Ontario Canada
    Age
    44
    Posts
    371

    Re: 03 STS rough IDLE P0300 & U1016 Code

    Could be wires, plugs or a coil. I think it's highly likely a wire/s. If you have an ohm meter you can check the resistance of each wire (i can post back the ohm range for you later). You can also do the same for the coil/s.

  4. #3
    Ur7x is offline Cadillac Owners Connoisseur
    Automobile(s): 02 STS
    Join Date
    Dec 2004
    Posts
    1,262

    Re: 03 STS rough IDLE P0300 & U1016 Code

    The 03 northstar is coil on plug... There are no sparkplug wires

    Clean the throttle body, and then clean the EGR Valve...
    Other then the idle... does it run OK... if so try replacing the Air bypass valve but on an 03 this shouldn't have failed... 00,01,02 and some early 03s have an issue with crank sensors which will cause a stall but generally not a lousy idle..

  5. #4
    mikeay's Avatar
    mikeay is offline Cadillac Owners Fanatic
    Automobile(s): 1996 Cadillac Seville STS
    Join Date
    Jul 2005
    Location
    Ontario Canada
    Age
    44
    Posts
    371

    Re: 03 STS rough IDLE P0300 & U1016 Code

    OK, apparently I know nothing about 98+ n*....

  6. #5
    ktraub is offline Cadillac Owners Member
    Automobile(s): '03 STS w/Nav, '93 SLS
    Join Date
    May 2005
    Location
    So, MD
    Posts
    59

    Re: 03 STS rough IDLE P0300 & U1016 Code

    UR7x, can you point me to a howto for cleaning the throttle body and EGR?
    Also, any idea what caused the U1016 code? Could it have been when I cleared the codes?

  7. #6
    ktraub is offline Cadillac Owners Member
    Automobile(s): '03 STS w/Nav, '93 SLS
    Join Date
    May 2005
    Location
    So, MD
    Posts
    59

    Re: 03 STS rough IDLE P0300 & U1016 Code

    Oh, and yes it does seem to run OK above idle (Except for WOT), although there is a slight stumble when first accelerating off idle.

  8. #7
    Ur7x is offline Cadillac Owners Connoisseur
    Automobile(s): 02 STS
    Join Date
    Dec 2004
    Posts
    1,262

    Re: 03 STS rough IDLE P0300 & U1016 Code

    Cleaning the Throttle body is easy... use an old toothbrush... or your finger and a can of Throttle body cleaner (what else) its basically squirt, scrub, wipe... clean the front and the back of the throttle blades...

    However the fact that is is stumbling at idle and WOT sound like it could be the EGR valve... It is supposed to be closed in both of those conditions... buy an EGR valve gasket at the dealership and remove the EGR valve and check it for deposits.

    The "U" codes are normal and will appear from time to time... Ignore it...

    How many miles on the car? It could be a bad spark plug too...

    Or a vacuum leak... There is a vacuum line under the engine trim cover at the back that tends to rub at the elbow and can cause a vacuum leak but vacuum leaks are usually only apparent at idle.

  9. #8
    ktraub is offline Cadillac Owners Member
    Automobile(s): '03 STS w/Nav, '93 SLS
    Join Date
    May 2005
    Location
    So, MD
    Posts
    59

    Re: 03 STS rough IDLE P0300 & U1016 Code

    Well, it turned out to be the #3 coil so it took a coil pack (not covered by my Continental Gold warranty! Thanks guys!) and the #3 plug. Also cleaned the throttle body and the injectors.
    BTW, had a broken front motor mount which Continental Warranty also DID NOT COVER! GRRRRR!
    Anyway, thanks for the help guys!
    -Kev

  10. #9
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Location
    Woodstock Ill.
    Age
    66
    Posts
    72,368

    Re: 03 STS rough IDLE P0300 & U1016 Code

    Sounds like a great warranty. Hope you didn't pay too much for it.

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting