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Update.. Code 12 ? what's it mean?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rocko, Nov 11, 2001.

  1. rocko

    rocko 1/2 ton status

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    Update.. Code 12 ? what\'s it mean?

    Okay... In reference to my post for a code scanner.. I used the paper clip trick given to me by Bigray71..
    I got a Code 12.. One Flash, followed by 2 short flashes after a long pause..
    What's that telling me?
    Took my air cleaner off, and the truck run's much better... could it be restricted airflow? I'm trying to narrow it down since I have to be back to work tomorrow..
    Any help would be greatly appreciated as alway's...
    Thanks guys..

    I haven't failed, I've found 10,000 ways that don't work. www.rocko.rockcrawler.com
     
  2. Stoopalini

    Stoopalini 1/2 ton status

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    Re: Update.. Code 12 ? what\'s it mean?

    Hey Charles,

    The ECM should flash a cdoe 12 three times just to let you know it is in a diagnostic mode. This is a normal code.

    After the 3 code 12 flashes, if there are any codes stored in the ECM, they will then be flashed. So, plug the paper clip in, turn the key, and wait until the light flashes a code 12 three times. Then if no other codes are flashed, there are no problem codes stored in the ECM.

    Later man, and congrats on the marriage!!! [​IMG]

    Thomas.

    -- '84 1-Ton Blazer --
    When the goin' gets tough,
    the tough go 1-Ton [​IMG]
     
  3. Chris Demartini

    Chris Demartini 1/2 ton status

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    Re: Update.. Code 12 ? what\'s it mean?

    <font color=blue>Hes right. It should flash 3 times to show its in diagnostic mode, then any stored hard codes will flash. If it still comes up, code 12 is no reference pulse from the distributor
     
  4. rocko

    rocko 1/2 ton status

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    Re: Update.. Code 12 ? what\'s it mean?

    Okay.. which plug's should the paper clip be in ?
    The two upper left terminal's? or the two upper right terminal's?
    Thanks for everyone's input so far.. Hope I can narrow it down before today to get it fixed.

    I haven't failed, I've found 10,000 ways that don't work. www.rocko.rockcrawler.com
     
  5. rocko

    rocko 1/2 ton status

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    Re: Update.. Code 12 ? what\'s it mean?

    Okay.. got the 3 Code 12's..
    Then it went to a 3 flash pause then 2 flashes..
    3 pause 2.
    What does this mean?
    Stoop.. my cell phone is 512-565-0438 if you can call me w/ the problem..
    Thanks in Advance.

    I haven't failed, I've found 10,000 ways that don't work. www.rocko.rockcrawler.com
     
  6. Chris Demartini

    Chris Demartini 1/2 ton status

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    Re: Update.. Code 12 ? what\'s it mean?

    <font color=blue>Code 32- EGR system.

    EGR solenoid should not be activated and vacuum should not be reaching the EGR valve. It says the diagnostic switch should close at 2 inches of vacuum. When you apply vacuum the switch should close. Also check if the EGR is sticking
     
  7. Stoopalini

    Stoopalini 1/2 ton status

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    Re: Update.. Code 12 ? what\'s it mean?

    Definitely sounds like an EGR problem. Your symptoms and the code both point toward it. Make sure it's not stuck like we talked about.

    Here is a link to a page that shows the GM ECM code breakdowns. There are other sites out there for this, but this was the first one I found when I searched.

    <a target="_blank" href=http://www.iroc-z.org/tech/troublecodes/>GM ECM Code List</a>

    Here is a snippet from that web site on what to do with a code 32:
    -------------------------------------------------------------
    Circuit Description:
    The EGR valve vacuum is controled by an ECM controlled solenoid. The ECM will tuen the EGR "ON" and "OFF" (dity cycle) by grounding CKT 435. The duty cycle is calulated by the ECM based on information from the coolant and mass air flow sensor and engine rpms. There should be (NO EGR) when in park or neutral when TPS input is below a specified value or when TPS is indicating wide open throttle (WOT). With the ignition "ON", engine stopped, the EGR solenoid is de-energized and, by grounding the diagnostic terminal, the solenoid is energized. Diagnostic switch will close when the EGR valve opens and exhaust gas is present at the switch.

    Test Description:
    Code 32 means that the EGR diagnostic switch was closed during start-up or that the switch was not detected closed under the folllowing conditions:
    Coolant temperature greater than 80 degrees Celcius (176 degrees Fahrenheit)
    EGR duty cycle commanded by the ECM is greater than 48%
    TPS less than wide open throttle (WOT), but not at idle
    Codes 21, 22, 23, 34 are not present
    1-This test will determine if the ECM set the code due to CKT 935 being grounded on start-up.
    2-This test checks if there is any faulty switch or ECM.
    3-This test will check for a possible open in CKT 935.
    4-By grounding the diagnostic terminal, the EGR solenoid should close and allow vacuum to be applied and the vacuum should hold.
    5-This test will determine if the electrical control part of the system is at fault of if the connector or solenoid are at fault.
    6-By plugging the EGR valve side and ungrounding the diagnostic terminal, the solenoid valve should open and allow vacuum to bleed off through the vent.
    7-With the engine running and vacuum applied to the valve, the valve should move to the fully open position.
    8-Due to this engine using a negative back pressure valve, the valve should close when the engine is cranked over.
    -------------------------------------------------------------

    Later,

    Tom.

    -- '84 1-Ton Blazer --
    When the goin' gets tough,
    the tough go 1-Ton [​IMG]
     
  8. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: Update.. Code 12 ? what\'s it mean?

    So put a plate over the EGR hole and you'll be good to go. :)

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  9. rocko

    rocko 1/2 ton status

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    Re: Update.. Code 12 ? what\'s it mean?

    Found the problem.. along with 2 others..
    EGR valve was all clogged up with Carbon deposit's.. preventing the diaphram from opening and closing.. So cleaned that with carb cleaner and WD40 and put it back on. Ran much better..
    Still idling real rough.. So I figured I'd check the plug's.. 3 of the 8 Plug's were loose enough to turn by hand and two of the plug wire boot's were dried out and cracked causing arching.. Replaced plug's with Bosch Platinum's and had two extra plug wires laying around..
    Truck feel's brand new again..
    Thanks for the EGR code's guy's...
    Now my Service engine soon light no longer come's on... [​IMG]

    I haven't failed, I've found 10,000 ways that don't work. www.rocko.rockcrawler.com
     

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