How to test for a bad ECM

Discussion in 'GM Powertrain' started by slimyguts, Nov 20, 2010.

  1. slimyguts

    slimyguts New Member

    87 Burban. Some issues that I think may be related to a bad ecm. Most of all when jumpin the ecm connector under the dash I can no longer get the ecm to go into test mode and blink the trouble codes. Worked before, but now nothin.
  2. Not good. What other symptoms are there? I never tested one per say, just hit the local U-Pull it and grabbed a used one to replace it whenever I thought that was the problem, not that expensive. Main thing is you got to test evreything and leave the ECM as the last option. Some auto parts stores have a free scan service and could tell you what the problem might be..... :wink:
  3. slimyguts

    slimyguts New Member

    87 burban 350 TBI auto 4x4 550k
    started with fuel pump issue. Hard to start. Must crank for about 30 - 4- seconds to start. Has spark no fuel. When key on fule pump does not run for the 2-4 seconds like normal. When it finally starts and I shut it off, the pump continues to run for about 80-90 seconds. Did this 5 - 6 times in a row. Check engine light came on a few times friday while driving but cannot get codes out. Looking at other sites like this (sorry all you die hards) and others have said they replaced the ecm. I want to test it first, if bad replace. Dont want to take any $$ from fishin and huntin fund unless its a necessary part. And it looks to be quite a bitch to get too.
    Last edited: Nov 20, 2010
  4. stephan

    stephan Rockstar 4 Years 5000 Posts

    Slimey, I don't think there are any checks @ our "mechanic level" for the ECU. It will have to be buy & try or get scanned @ Autozone or one of the other auto repair shops like Northport said.
    I answered your other thread on fuel pump continues running on 90 seconds...
  5. slimyguts

    slimyguts New Member

    So I got curious about this connector under the dash. Terminal A is to be a ground and Terminal B is the diag. port. If Terminal A is a gorund, why is my multi meter reading 8.7 v ?

    ---------- Post added at 04:24 PM ---------- Previous post was at 02:27 PM ----------

    Another observation. When turning the key to the on position and the ecm performs the POST (evidence by watching the SES light come on, then blink off then on solid until engine is started) the engine will start within 2 seconds. Then for no reason I can find, the key is turned to the on position, the ecm will not perform the POST (evidence by the SES light staying on solid) and it will take 30-40 seconds of cranking to start the engine.

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