I have a 98 F-body with 411 pcm. I'm running an aftermarket fuel cell and sending unit. I'm trying to get my fuel gauge to read correctly but it reads full all the time. After some searching, I found that I need to enable PWM and set it to 140.63 hz. So dumb question how do I enable PWM and set it to the 140.63. I can't seem to find and enable/disable setting anywhere.
Thanks
Magic trick of the day: Hit CTRL+N and type in 'pwm'.
screenshot.17-06-2023 19.46.17.png
Of course this is assuming that whatever OS you're using in your swapped PCM has this setting. Since you didn't post your file...
i love magic
Yeah I don't have that. So im guessing im SOL on getting the 98 fuel gauge to read with my OS. That suxs. I did verify that the PCM is reading accurate voltage empty to full from the sender. Its a 99 Camaro OS I believe.turboTA-t562BAR.2.hpt
Are there any other options for getting the 98 gauge to read with this OS?
Why use the '99 OS? I think the '01-'02 (12212156) has much wider support, more parameters because there are more users over the years asking for things to be added. 12212156 is where my screenshot came from.
I would update to the 02 OS however all the stock tunes I can find are written with an update version of HPT software. I cant update the software because it will not work with my old cable.
From my searching I think I have 4 options.
1. Aftermarket fuel gauge
2. Purchase another 411 PCM 2002 OS, then license and upgrade to 2 bar OS, copy tune over to that
3. Possibly find someone with Tuner Cat, supposedly that can enable the PWM on the 99 PCM
4. Say fuck it and just keep the tank full
If anyone knows a different work around, please let me know.
Last edited by turboTA; 06-20-2023 at 08:58 PM.
What is the output of the sending unit? 0-5V?
Im getting 1.1-2.5V on my scan toolOriginally Posted by SiriusC1024
According to a search thats pretty close to what the factory sending unit should read as well.
https://ls1tech.com/forums/fueling-i...ls-inside.html
https://forum.hptuners.com/showthrea...ues-on-99-swap
Take a look at this thread it may help.
IIRC the 98 cluster get signals differently than 99-02.
Last edited by slarsen47; 06-18-2023 at 05:01 PM.
So after trying 3 laptops with the latest stable version and multiple firmware update attempts everything is working properly now. And luckily I now have the PWM enable feature with the 99 OS. Fuel gauge is working now!
So to clarify, you have a 1999 411 PCM with a 1998 dash cluster and everything works.
The reason I ask is because I have a solid roof 1998 that will soon have a 6.0 with a turbo and 4L80e and I will be using a "12212156" 411 PCM and do the same 2 bar update and transmission segment swap as I did with the procharged 4L60e car.
I had been under the impression that the 1998 cluster was backwards compatible, but not with 1999 and newer PCM's.
Something to do with the communication signal.
Yes I Have a 98 car/cluster with a 411PCM. Mine is a 99 2bar OS. I’m running a Rhodes Race Cars 17 gallon fuel cell with their 10-180ohm sending unit. I have a 62ohm resistor on the factory purple fuel sending unit wire. Which puts me close to what the factory 99+ sending unit would put out for ohms and voltage. Verified that with multimeter and scan tool.
As far as tune. Invert the “Gauge Output” table, enable “Gauge uses PWM” and set “PWM Gauge Frequency” to 140.63hz.
Everything seems to work like it should now. You could probably play with the output table some and get things super accurate. But this setup for me works as close as the factory setup did so I’m good with that.
Your harness must have been changed because you cannot just plug 98 harness into a 99 and up PCM without doing a lot of re-pinning.
The following link explains.
http://www.mrk-motorsports.com/wp-co...o-1999-PCM.pdf
Yes I repinned the harness I assumed that was a given.
I think you did pretty good work. Thanks for sharing the solution for other people.
Guys I have a question. I have a 96 k1500 with an 0411. I set my pwm hz to 240 to completely eliminate any erroneous gauge needle movement. Do you think that could damage anything? I can't imagine it would, but I'm not sure. I started at 60hz and it fluttered like crazy, went to 120hz and it calmed down almost completely. 240hz and it's perfectly still. Still works though.
Thoughts?
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