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Thread: 2006 GTO LS2 6.0 in a classic car

  1. #21
    Tuning Addict blindsquirrel's Avatar
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    Yes. Getting the throttle working should be first priority. A no-start condition won't make the throttle not work, but a throttle condition can cause a no-start. There are lots of threads like this, too. So it's not just you.

  2. #22
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    Quote Originally Posted by blindsquirrel View Post
    Yes. Getting the throttle working should be first priority. A no-start condition won't make the throttle not work, but a throttle condition can cause a no-start. There are lots of threads like this, too. So it's not just you.
    Thank you for the help and the diagrams to go off of. I'm still battling the throttle body not opening, in relation to the APP. Getting a PO641 Code as well. As far as the two 5-volt ref. on the APP should they both be 5-volt? Ive heard and read that one is at 5-volt as the APP is pushed one 5-volt goes to around 1.5volts the other 5-volt starts low and does the opposite, is this true? I have 5-volts at the APP #2 and 1.5 volts on the APP #6.

    Again thank you for your help and insight to this problem.

  3. #23
    Tuning Addict blindsquirrel's Avatar
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    Don't confuse the 5v ref lines with the sensor return lines - this is set up as two completely independent 3-wire sensors that just happen to be mounted in the same plastic box. Two independent 5-volt reference, two independent low references (grounds, provided inside the PCM itself), and two independent sensor outputs. The 5v refs should always be around 5 volts no matter what, the two low refs always ground, and the two sensor returns vary with pedal position. And the two sensors both increase as the pedal goes from idle to WOT, but they are NOT supposed to output identical voltages. Different platforms/PCMs/ECMs work different, some do sweep opposite directions, but this one does not.

    With the APP unplugged and key-on, you should have ~5v at #2 and #6, ground at #1 & #7, and something similar to ground at #3 & #5 (there is a pull-down resistor on those lines inside the ECM, they will be low with the APP connector not plugged in to the pedal).

    DTC P0641
    Circuit Description

    The engine control module (ECM) provides 5 volts to the following sensors:
    • The manifold absolute pressure (MAP) sensor
    • The engine oil pressure (EOP) sensor
    • The fuel tank pressure (FTP) sensor
    • The air conditioning (A/C) refrigerant pressure sensor
    • The accelerator pedal position (APP) sensor 2
    • The camshaft position (CMP) sensor (2006 Corvette and Cadillac CTSv 6.0 only)

    These 5-volt reference circuits are independent of each other outside the ECM, but are bussed together inside the ECM. Therefore a circuit condition on one sensor 5-volt reference circuit may affect the other sensor 5-volt reference circuits. The ECM monitors the voltage on the 5-volt reference circuit. If the ECM detects that the voltage is out of tolerance, DTC P0641 sets.
    Hmmm... note that this particular 5v supply leg feeds APP2, but not APP1, which appears to be working. Something in that list is pulling the 5v line down and affecting your APP2 - and MAP sensor. Unplug those sensors one at a time and see which one it is.

  4. #24
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    blindsquirrl, I cant thank you enough. Thank you so much for your help. I'm not exactly sure what I've done but it all works now. Its interesting how the APP system works, with the 5 volt and low refs. The problem was on the OPS sensor, I'm not sure why but i repined it a couple of times, ending up pinning it back to what it was, the throttle works and revs great.
    Thank you again for your help.
    Holden

  5. #25
    Tuning Addict blindsquirrel's Avatar
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    Just for future reference (reference? get it?), this list comes from the DTC descriptions for P0641 & P0651.

    5-Volt Reference 1 Circuit
    ? The manifold absolute pressure (MAP) sensor
    ? The engine oil pressure (EOP) sensor
    ? The fuel tank pressure (FTP) sensor
    ? The air conditioning (A/C) refrigerant pressure sensor
    ? The accelerator pedal position (APP) sensor 2
    ? The camshaft position (CMP) sensor (2006 Corvette and Cadillac CTSv 6.0 only)

    5-Volt Reference 2 Circuit
    ? The accelerator pedal position (APP) sensor 1
    ? The throttle position (TP) sensor 1 and 2
    ? The cooling fan speed sensor (If equipped)
    ? The crankshaft position (CKP) sensor (If equipped)
    Some other years/platforms call out which 5vref circuit is used for which sensors in the ECM pinout, and rarely if never in the individual diagrams.

    And if it makes you feel any better, there are mistaeks in teh GM diagrams too. This particular one isn't fatal, just a little confusing because of the leftover label that shouldn't be there.

    screenshot.04-09-2019 17.44.23.png

  6. #26
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    blindsquirrel, After I got everything working properly, I sent the harness and computer to the guy working on the car and he cant get the throttle to work. So... Can I just build him a different harness and use a 0411 pcm and switch it over to drive by cable, and put the gen 3 knock sensors in the spot where the gen 4 knock sensors, are and have him take it to a tuner in Vegas and have it all tuned?
    I guess my question is will an 0411 run the LS2 with the drive by cable throttle body?

  7. #27
    Tuning Addict blindsquirrel's Avatar
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    Gen3 specifics are outside my wheelhouse, but, as long as this is a 24x/1x LS2, any Gen3 computer will run it just fine once the Gen3 components are bolted on.