'95 K1500 Transmission/Check Engine Light

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by rdnkdrummer, Feb 16, 2010.

  1. rdnkdrummer

    rdnkdrummer Rockstar

    I read through all the previous threads I could find, and it seemed that no one else had the same issue(s) I'm having. I hope this isn't a repeat. If so, Please point me int he right direction.

    Sometimes (maybe once a week, maybe 3 times a day), the check engine light will come on when I start the truck. I haven't been anywhere near Autozone when it does to check code. But when the light is on, the transmission shifts late & very hard, but not slipping (like the old TH350 tranny's would do if the vacuum wasn't connected). Also, it seems like the engine doesn't run the same either. In park, when you gas it, there's a hesitation. 9 times out of 10, if I turn it off for a few seconds, and restart, the light is usually back off again, and everything is normal.

    I know I need to check it at the autozone with the light on, but i'm afraid to drive it very far like that because I don't have money for a new transmission, so I usually turn it off and back on.


    Thanks in advance!

  2. jedepsub

    jedepsub Rockstar

    You properly have one of these codes.

    P1870, P0748 & P0719

    I had the same problem a few months ago, took it to a transmission shop. Had to have it rebuilt.
  3. rdnkdrummer

    rdnkdrummer Rockstar

    not what i wanted to hear, but thanks :) I don't understand the engine not running right part though...very strange.
  4. jedepsub

    jedepsub Rockstar

    Take it somewhere to have it scanned first & let us know what codes you have.
  5. SupplySgt

    SupplySgt Rockstar 4 Years 500 Posts

    If it's a 95 then it'll be OBDI. To pull that code you need to jump the diagnostic port. Take a wire or paper clip or something like that and use it to connect the 2 holes on the top right of the port. Turn the key to the "on" position (but don't start it) and the Check Engine light will flash to indicate numbers. It'll start out with code 12 which will show up as "flash" pause "flash flash". It'll do that a total of 3 times. After that it'll give you the code (or codes if there's more than one). It'll flash the number of times corresponding with the first digit, then a pause, then it'll flash the number of times corresponding with the second digit. Each code will be flashed a total of three times. All OBDI trouble codes are two digits. Once it's given you all the codes it'll flash code 12 three more times to let you know it's done. The code is likely stored in the PCM so try that first chance you get and then post up what you find. I have the Haynes manual so once we have a code then we'll know what you're dealing with. Hope this helps and we can get it figured out.
    1 person likes this.
  6. redditt

    redditt New Member

    I'm having the same problem with my '95 K1500 Suburban. The only difference is that my brother-in-law just rebuilt the transmission ab out 12,000 miles ago. It's been doing this ever since (and possibly before since we bought it from the rescue squad). It's at 262,000 miles now; it had the motor, tranny, and transfer case all rebuilt within the last 60, 000 miles. Mine only seems to do it on cold days and will continue to do it even after it's been turned off and back on until it's warmed up all the way. :grrrrrr:

    It'll help a ton to know what the heck is going on with this thing. I had one guy suggest to do a tune-up since his '96 did the same thing until he did a tune-up. He suspected a cracked plug wire or plug that would cause a dead cylinder. The other thing I've heard is the torque converter, but we replaced that with the rebuilt tranny.:neutral:

    I'm new at working on cars. I've worked on motorcycles all my life. Pictures would help a lot with the directions of putting in a jumper to get the codes. :great:
  7. jedepsub

    jedepsub Rockstar

    Could be your valve body on the transmission.

    The valve body is the control center of the automatic transmission. It contains a maze of channels and passages that direct hydraulic fluid to the numerous valves which then activate the appropriate clutch pack or band servo to smoothly shift to the appropriate gear for each driving situation. Each of the many valves in the valve body has a specific purpose and is named for that function. For example the 2-3 shift valve activates the 2nd gear to 3rd gear up-shift or the 3-2 shift timing valve which determines when a downshift should occur.
  8. Joeairforce

    Joeairforce Epic Member 5+ Years 100 Posts

    Here..... :great:

  9. redditt

    redditt New Member

    Thanks for the pics! That helps a lot.
  10. redditt

    redditt New Member

    Well, I know that's not mine then. Mine will upshift hard and late between every gear when the light's on. That's good to know though.

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