segment swap in COS5

[B18B1LS1]

Trying to do a fuel system segment swap to get my fuel gauge working on my 98 to 99+ pcm swap. Everything seems to be copying over fine, and all tables and parameters are changed back to my 98 info. But the gauge still isn't working, just stays maxed out. Is the problem that I needed to do the segment swap before going with a COS? Do I have to revert back to my original GM OS then segment swap, and then start over on my COS5? Thanks guys!

Jeffrey

[ScarabEpic22]

I havent tried it, but the easiest thing to do would be to load your current COS file and try to compare it with the base file you need the fuel segment from. The base OS' must be the same (pre-COS upgrade file and source file), even then I dont know if the tune tool can do it. If you get a "cannot load calibration with alternate OS" or similar error, have to go back to the base file, seg swap it, then COS upgrade.

[B18B1LS1]

I don't get any errors, it says that it copies and loads over fine. I'm doing the standard 02 Express Van segment swap that everyone does, but must be missing something!

[joecar]

Try playing with the fuel level table, see if you can make the gauge move.

[B18B1LS1]

Nope, no dice. I scaled the table up and down by 50% and 150% and never saw a change in the needle reading full

[joecar]

What happens if you unplug the fuel level sender...?

[B18B1LS1]

Hmm, not sure. It's a '98 so I'll have to get under the car to pull that plug. Hopefully I'll have some free time tomorrow.

[B18B1LS1]

Popped the plug off, the gauge doesn't move, stays maxed out.

[joecar]

What happens if you short the pin in the connector to ground...?

~ posted by phone ~

[B18B1LS1]

Still doesn't move when grounded. Ohms show 82.3, car has probably 1/3 tank in it. Are you thinking this might not be tune related since it seemed to load the segment swap?

[joecar]

I'm trying to see if you can get the gauge to move at all.

[B18B1LS1]

So far, nothing has affected it, stays pegged. Ended up running it way too low today not paying attention and almost ended up on the side of the road. Added 15.7 gallons, oops!

[joecar]

Try doing the full flash again.

[B18B1LS1]

Did a full flash, still nada

[joecar]

...
Do I have to revert back to my original GM OS then segment swap, and then start over on my COS5?
...
You shouldn't have to, but go ahead and try that ^

[B18B1LS1]

Would I just full flash right back to the stock 02 OS, then swap in the fuel segment and do a calibration flash and see if it works? If it does then start copying over all my current tune tables?
And if it doesn't work and I want to get back to where I'm at now so the car is at least driveable, I can just full flash my current COS5 tune right back in no problem?

[joecar]

Save your current COS5 tune.

Then full flash to the GM tune, do the fuel segment swap, do a full flash, and see if gauge works.

If it does, do the empty COS5 full flash, read it back (do the sanity edits) and save as new file, see if gauge works.

~ posted by phone ~

[B18B1LS1]

Ok, just wanted to make sure! Thanks Joecar

[B18B1LS1]

Still didn't help unfortunately. I'm not sure how I made something so simple, so complicated! I'm wondering if the sender crapped out or the wiring is jacked up somehow

[B18B1LS1]

If I'm reading the electrical diagram correctly, I should be sending 5v down the purple wire to feed my sender, my multimeter is showing only 1.2v, hmmm. Does this fuel segment stuff affect the voltage being sent to the sender in any way?

[B18B1LS1]

Scratch the last thought, it seems like my Ohm reading and my 1.2v reading match up. The pcm uses variable voltage to interpret gallons and that all seems inline. So now I'm back to thinking its pcm/tune again. Maybe!

[joecar]

If I'm reading the electrical diagram correctly, I should be sending 5v down the purple wire to feed my sender, my multimeter is showing only 1.2v, hmmm. Does this fuel segment stuff affect the voltage being sent to the sender in any way?Which circuit diagram are you looking at (year/model/vehicle)...?

[B18B1LS1]

I only have the '98 manuals, 1998 Chevy Camaro v8

[Doc]

I take it you are using the 98 gage cluster? If so, the calibration of the fuel sending unit is about 180 deg out of phase with ( How it looks in the tune) the "newer" COS you are using. Had to play with road runner plenty of times setting up fuel sending units on fuel cells and other 98s.

[B18B1LS1]

Yes, 98 gauge cluster. I've tried scaling the calibration up/down/inverted just to try and get the gauge to move. But it seems no value affects it so far

[B18B1LS1]

Wanted to update you guys, it's fixed! I'm embarrassed to admit it, but it was my fault the whole time.
I pulled the pcm out (behind the dashboard) to backprobe the pins and see what was being sent to the gauge. Turns out there was no wire in that slot at all. When I did the pcm swap a long time ago, one of the instructions was "Red 36 to Red 38, Test First". I guess I took that as test the pcm swap and if it works don't bother with that wire. Since everything worked I had it bundled with the other unused wires and never gave it a second thought.
Fast forward a few months later to now, when I went back to get the gauge working, I assumed a segment swap was all I needed. It never crossed my mind I had unused wires from the pcm swap.
Moral of the story:
CHECK YOUR WORK FIRST
Thanks for all the help anyway guys!

[joecar]

Stuff happens... Thanks for the update.