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Thread: fuel gauge didn't work after ecu swap

  1. #1

    fuel gauge didn't work after ecu swap

    Hi, I swapped in a engine, trans, and t-case along with the ecu ecu from a drive by cable yukon 2500 with a lq4 into a 1999 silverado and when I did the fuel gauge stopped working. Right when you turn the key on it works for a couple of seconds and then it drops down all the way to empty. It is also throwing a few codes like low coolant. Does anyone know if there is anything I can do to fix it, or is it just some sort of incompatibility thing? thanks

  2. #2
    Advanced Tuner mbray01's Avatar
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    I would be checking the wiring, specifically at the bulkhead for the under hood fuse panel. If the 99 was a v6, those are usually different
    Michael Bray
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  3. #3
    it had a 5.3 in it stock. I didn't do any wiring just a ecu swap. And also I tried swapping the stock ecu back in it and it works with the stock one.

  4. #4
    Had same problem with my 98 s10 when I put a junkyard PCM into it. Didn't have a tuner back then to figure it out. Best guess is what Embray said, check wiring. Probably a pin out issue between PCM's or a resistance value thing. Get a tune from repository or pull the tune from the 5.3 PCM and compare it to the 6.0 tune. Could also be the Yukon had dual tanks and needs BOTH tank senders to calculate fuel gauge output. HPT should be able to tune that out if that is the case.

    To add, you could probably run the 5.3 PCM and tune it for the 6.0 values needed.
    Last edited by vettemakesemwet; 1 Week Ago at 01:56 PM.
    03 Z06 stock.......for now
    05 Siearra 5.3 daily
    I have realized that tuning is a rabbit hole. No problem diving down this hole, in fact I jumped willingly. Just want to avoid hitting every ugly rock or root on the way down it.

  5. #5
    I was planning on using the 5.3 ecu to begin with, but we swapped in a 4l80 and I couldn't find any tune files that came stock with a 4l80 with the same OS to do a segment swap. So that is why I used the ecu from the yukon. But I swapped the stock ecu back in its place and the gauge works. Also the guage works for a couple of seconds and is accurate then it goes down to empty even though its not. Not sure if the yukon has dual tanks, but I would be almost positive that it is single. Thanks for the input though.

  6. #6
    Posting the tunes from each PCM would let us see what is happening. Best advice after that is hit the wiring diagrams for fuel sender into PCM for each vehicle and see what is different. Gauge and tank data in in the fuel system tab in the editor. See what doesn't compute.
    03 Z06 stock.......for now
    05 Siearra 5.3 daily
    I have realized that tuning is a rabbit hole. No problem diving down this hole, in fact I jumped willingly. Just want to avoid hitting every ugly rock or root on the way down it.