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Thread: Pcm ground

  1. #11
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    Wow, my whole post is gone again... looks like the edit issue I am.having is actually deleting...

  2. #12
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    Sorry, guess I said it wrong, I dont actually get an ses right, then ight comes on for bulb test when ignition is first turned on.
    I have hooked up scan9495 and whack, I have no codes, however I am seeing no injector pulse width. Didnt check.dornapark as i ran out of daylight.
    Internet can be a bit misleading as I have read in a couple of places that pcm need to see at least 4 psi to activate injectors etc, but from what I read on shoeboxes site, none of the connectors at pcm go to oil pressure sensor, I have an adapter screwed into op sensor port with jag sensor screwed in and the wire goes straight to the gauge. The original op wire ( tan) is tucked into the harness loom, so no big deal if I need to pull it out and hook it to something.
    Other things I am reading are pointing to the opti, however I am pretty confident it's not the issue ( I could be wrong, wouldnt be the first time) as it was sent off to the optidoc guy on ebay and he refurbished it and sent video of it hooked up to oscilloscope and working..

    Any further insight greatly appreciated

    Thanks
    Darren

  3. #13
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    Kept hitting back and my post was still there that way, so copied and pasted, sorry if it's a duplicate now

  4. #14
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    Additionally I am reading a vats issue, but pcm was tuned by Moe Bailey, supposed to have deleted vats, but I don't know how to double check that..

  5. #15
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    The 94/95 F-Body LT1 control does not have the low oil pressure interlock. The Corvette LT1 does.

    What is the VATS issue? The PCM is looking for a 60Hz signal from the theft deterrent module (TDM). Doesn’t turn on the fuel system until it receives that signal. That requirement can be “programmed out”. Do you have DTC 46?

    Do you have spark at the plugs? ...... at the coil wire? When the engine is cranking, does the tach needle move upwards 200-300 RPM? Did you interface the PCM signal with the Jag's tach?

    Testing for Opti signals:

    http://shbox.com/1/4th_gen_tech2.html#opti_test

    Is the Opti possibly the second generation (95-97 F-Body) “vented” unit? That has a different socket for the harness connector, and doesn’t match the 93/94 “unvented” harness connector.

  6. #16
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    I have no codes at all, (per scan94/95) , didnt get to check for spark as it was getting dark and I had no helper, that's on tonights checklist.
    Only reason I mentioned vats was because I read that it can cause issue i am having, however like I said, it's supposed to be deleted in the tune. Is there a way to check for that?
    I will also check the opti with the shoebox link, will post again when I have all that info.

    Thanks for your time!

    Darren

  7. #17
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    Opti is 1st gen but was converted to vented by opticdoc.
    Had no movement at all from tach, and yes I had to add a resistor and its tied into pcm output.

  8. #18
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    Ask Moe to confirm he deleted it. But if the PCM isn’t setting DTC 46 and you don’t have a TDM in the circuit, it sounds like it's been programmed out. How did you address the other part of the VATS system that runs the starter solenoid relay power through the TDM to the starter relay (TDR), so the TDM can verify the key resistance before it allows the starter to engage? I assume you just wired it to bypass, deleting the TDM.

    As far as codes for the Opti pulse signals, if both high and low res pulses are missing, the PCM can’t set the DTC 16 code for the low res signal (the one required to allow the engine to start) because it has to count high res pulses to determine if the low res pulses are missing. Run the Shoebox checks.
    Last edited by Injuneer; 02-12-2020 at 08:52 AM.

  9. #19
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    I simply brought the purple starter solenoid wire from the 4 wire black connector inside, back out and plugged onto existing jag starter relay. Do i need to add something else?

  10. #20
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    If it cranks the engine when you turn the key to “start” it’s done right.

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