08 superduty fuel level gauge issues

leavnon3rd · June 4, 2014

just to give some quick backround on this vehicle in jan 14' another tech replaced both sending units ( dual tank) and a IC

I have a 2008 f550 6.4 that will only read the front tank. When i flip the tranfer switch to the rear the the valve on the frame i know switches over and pulls fuel as is should but the guage still mirrors the front. heres a list of tests ive done and i cant understand why it wont read the rear tank on the IC.

front tank is full and reads 12ohms at the sending unit and also at the IC connecter (c202)

the rear tank has 10 galons init, and reads 104 ohms also from the sender and at the IC connector (c202)

i swapped in a dummy sender on the rear tank and theres ZERO change, yet when i put the dummy sender on the front tank i can get it to sweep acordingly all while the transfer switch is still on the position for the rear tank. If i unplug the rear tank nothing happens on the IC, i disconnect the front and it goes right to empty and the low fuel chime is shown

i swapped out another transfer switch for a known good spare i have, same concerns.

the transfer switch when on rear tank sneds a 12v signal to the IC (pin 23) telling the IC to switch sending units, it carries over 12v;s and th wires ohms good ( itll even keep a test light lit)

i ensured the pins on the IC are making a full and good ocntact with the connector.

SO i condmened the cluster since im geting correct info from both senders and the signal to switch, i install and program the new cluster using asbuilt info and it does the same god damn thing.

ive ben banging my head for 2 days now feeling like a dummy i need help here guys.

thanks.

8WA Sman · June 4, 2014

If the rear mirrors the front and if I understand your test correctly...I would check the IC calibration data. Did the tech use PMI or As built?

I am assuming if there was codes they would be posted.

leavnon3rd · June 5, 2014

yes ive dealt with issues easily enough when there is a dtc present, But there is NOT on this truck. my ids pulled all the files it needed off of oasis ( assume its asbuilt then?) I programmed the IC, then reflashed the PCM and then pats ( this truck has pats disabled, police dept.)

i looked for IC updates/ later calibrations and it claims there wasnt any.

Aaron · June 5, 2014

There is a setting for dual tanks in programmable parameters screen isn't there?

Aaron · June 5, 2014

Look under the Oshkosh/Plasan Sand Cat option.

Cetane · June 5, 2014

As-Built shows the correct configuration for that vehicle so assuming IDS pulled the info from the database and not the old cluster, it is correct.

leavnon3rd · June 5, 2014

I have off for the next few days so itll give my head some to heal lol. Ill manually enter the as build code on monday and see what happens(i assumed the old file was crrect). I let the ids pull the old file and thinking about it more its possible the reae tank never read after initial repair. Sorta makes sense now since the last tech was a bit of a hack and this truck came in on the hook airbound

Ill keep you guys updated

leavnon3rd · June 9, 2014

After talking to cetane (thanks again) i pulled the asbuilt file and programmed it rather then the ids pulling it and it did the trick.

So this means this guy has been driving around since january with out it working

Thanks again fellas

Cetane · June 11, 2014

Any ideas how the takeout cluster got a bad config? Was it a used unit that didn't get updated?

leavnon3rd · June 11, 2014

I asked the tech who installed it in january, it was a repaired cluster and he claims he programmed it but didnt remember. This particular tech has been on the down slope for a while so i cant trust anything he says. But i do know for sure the cluster was a repaired one from ford. It has a tag on the bottom that said. It was from jan of 14'

Thanks again guys this site rocks