We should update the GIF on the front page to t he revised version found here: http://www.thirdgen.org/techboard/po...82-post40.html
Notably, the P/N switch is updated. I've been beating my head against a wall because my IAC isn't working right. Because I don't have the wire hooked up, because it was not on the sheet. It was not grounded so it thought it was in drive and would not do the pintle thing.
Thank you and done!
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
I have checked the pinout on the first page and cross checked factory pinouts from C/K and S/T vehicles using the same PCM family with manual transmissions. I see no park/neutral switch input or grounded signal wire listed in the OEM diagrams. Also, the two factory diagrams I have show both VSS and trans speed signals connected to the pcm in manual trans applications.
Does anyone have confirmation of P/N input on E5, or of the results of not including the VSS / trans speed signal on F13?
Thanks
Last edited by 1project2many; 08-13-2012 at 07:04 AM.
The '7427 does not use a nuetral safety switch input.
What it does use is the gear select inputs to determine what gear the trans shifter is in. I don't remember the combination of on's and off's of those three inputs to detect what gear is selected, but I know it's in some of the EFI manuals from OTC and Snap On IIRC.
The man who says something is impossible, is usually interrupted by the man doing it.
Right. Whoops... this was specifically related to manual trans applications. Previous post edited for clarity. :)
On my '427 PCM schematics, A5 is Distributor Reference Low (Ground). I personally don't like the idea of grounding the P/N wire to Ground. On the '7747 to '427 PCM conversions I've done, I covered the P/N wire with heat shrink tubing and zipped tied the P/N wire to the harness.Originally Posted by 1project2many
The challenge I see to using a '427 PCM without a VSS is being able program which Spark / Fuel tables (Near Idle / Off Idle) for the PCM to use. I'm thinking without a VSS input, the '427 PCM will always think the vehicle speed is ZERO MPH. The '427 PCM could be programmed to switch from near idle / off idle, Spark / Fuel tables by TPS% only? I've never tried using TPS% only programming on the '427.
dave w
The pin in question was E5. Range switch C. I need a better proofreader. :(
That matches the manual trans wiring diagrams.On the '7747 to '427 PCM conversions I've done, I covered the P/N wire with heat shrink tubing and zipped tied the P/N wire to the harness.
Those diagrams also show two signals from the DRAC. One is VSS and one is trans speed. The "possible symptom" for a faulty trans speed signal on F13 is "fuel cut." I have a 4k ppm VSS signal to supply. I do not have a 40 pulse/revolution trans speed signal.
The '7747 is a 2K PPM VSS. The '427 is happy with a 2K PMM input to pin F13. The only time I needed 40 pulses / revolution was for an electronic overdrive transmission conversion.
dave w
What is the normal input from the VSSB to pin F13 on the '7427? Some sources say 2k PPM, but others say 4k PPM. And when do you need to set the "Output Speed not from DRAC" flag?
Last edited by belaw; 08-13-2012 at 06:12 PM.
I've done this and is working quite well. I did it because someone elsewhere said it could not be done. That said I will never do it again to save $80 for a VSS... way to many hours tuning to work out bugs...
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
Posting Permissions
Reply With Quote
Bookmarks