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Thread: No output from VSSB to speedo -7427 ecm

  1. #1
    Electronic Ignition!
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    No output from VSSB to speedo -7427 ecm

    Changeover to 4l60e & f.i. on olds 403 w/95 c1500 truck bjyk 16197427 ecm. I have a factory scan tool & a digital oscilloscope.The B+& B- check good. The speed sensor output, & the vss buffer square waves on c11 & c13 look ok to me. The scan tool sees vehicle speed & the trans shifts ok. The speedo output on c15 is not there. I am at a loss as to why there is no vssb speedo output. Anybody have an answer ? Tried 2 vssb's - no help, but both work on my 94 s10 w/7427 ecm.
    Last edited by bar0403; 04-18-2019 at 01:48 AM. Reason: forgot info

  2. #2
    Fuel Injected!
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    Try C14. Some vehicles use C14 on the VSSB for speedo and some use C15, I think it has to do with higher voltage on the C14 but same 2000ppm signal.

  3. #3
    Electronic Ignition!
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    C14 has no output. C10 does have a square wave that is not being used. That will work for the speedo I am using. Is the C14,15 signal 2000 pulses per mile ?

  4. #4
    Fuel Injected!
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    Quote Originally Posted by bar0403 View Post
    C14 has no output. C10 does have a square wave that is not being used. That will work for the speedo I am using. Is the C14,15 signal 2000 pulses per mile ?
    Yes, C14/15 are both 2000 pulse per mile.

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