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Hey guys, I am swapping my 2003 C5 Z06 "P01" to a 2004 PCM aka "P59" in order to run flex fuel on the car. The hardware side of this has been covered in a few threads on here, but not much on the software or tuning side.
PCM
There may be others that work, but from what I understand this model supports *all* P59 features and also what the 04s used, so best to stick with what's known to work. Also used on 04 Tahoe and other flex fuel vehicles around then.
Service #: 12586243
Hardware #: 12583659
Harness/wiring
P01 has Blue and Red harness. P59 has Blue and Green. Obviously this will vary a little bit from year to year. Find a pinout for your car and compare to 04...highlight all differences. Mine was 03 to 04 so it was relatively simple.
Blue connector: P59 has 4 additional ground pins: 24,27,64,67, grounded to G106 (engine, above starter).
Red/green connector: (1) Alternator pin needs moved from pin 52 (gray wire) to pin 75. (2) The O2 sensors on P59 are grounded to PCM so it can monitor heater circuit. B1S1 is pin 72, B2S1 is pin 74. (I didn't bother writing down rear sensors, but I can dig that up if needed)
Ethanol sensor: 3 wire pinout. +12V, ground and Blue pin 56 for signal
You have to grind down the red plastic connectors, to fit into the "green" connector on the PCM side. Easy 1 minute job with a dremel. Or buy/use the green covers. See pic below.
13577429: small, compact, short fittings, no mounting holes
13577394: full size, long fittings, mounting holes
13577379: full size, short fittings, mounting holes
I chose -429 to keep it small and it's the cheapest. Note that the factory style quick connect fuel fitting connecting to the "short fitting" models will be a pain to remove. It doesn't leave you enough space to fit in the typical fuel line disconnect tool. I had to cut up an extra one I had to make it work, but now I have one that will work in the future--no big deal. But it was looking like it was going to be a tight fit for the lines I had ordered, so I wanted to keep the sensor as small and compact as possible. I ended up just zip tie-ing mine to the brake fluid reservoir.
I found those Russell fuel lines to work great and I wanted to retain the OEM like quality/fittings with this all being right above the headers and such. Apparently it's an upgrade fuel line for the GTOs. PN 651120 is for the LS1, while PN 651121 is for the LS2 GTO and looks to be very similar or identical. -20 was basically the same length as the stock hose, just a 90 degree fitting on one end.
The pins should be labeled on the ethanol sensor, but I ran +12V to fuel pump fuse, ground to nearest ground point and signal to Blue Pin 56 as described above.
Tuning/Software
OK this is where the public information is lacking from I found, or at least not consolidated in one place
You have to do a VATS/BCM relearn procedure so your PCM/BCM will recognize and work together. HPtuners and EFI Live have this "command" built in to make it super easy and no drama. Otherwise if you're doing this on your own but not your own tuning, you will need to do the procedure outlined here: https://www.corvetteforum.com/forums...m-program.html
I don't think you need to, but I went ahead and changed the VIN on my PCM to match the vehicle.
It's best to use a 2004 Corvette tune file as your starting point to retain all car/Corvette specific functionality. If you segment swap from a truck, you lose functionality (like fuel gauge issues) and you also ensure the tune supports electronic throttle etc etc.
2004 Corvette tune files have flex fuel disabled by default. Not all flex fuel tables are exposed in Hptuners or EFILive (or DIY options like Tunerpro, from what I saw).
For example by default, you can see and see the ethanol timing adjustment table, but there is an unmapped Ethanol content vs timing bias table that is zero'd out on the Corvette tunes that need adjusted. You can put whatever you want in that ethanol timing table, but it's never to reference it.
You need a 2004 Corvette file that has been adjusted to enable flex fuel completely or define those "hidden" tables yourself and put reasonable values in them.
Operating systems: 12587603 is a really common one for the 1MB P59s and was also used for the 04 C5. 12592425 was released as part of the column lock safety campaign... not entire sure what it did, from what I can gather, something about an additional safety feature to make sure the cars couldn't be driven when the column was locked as an extra safety net. Either way it was an update that cars were offered back in the day.
I used a 2004 Tahoe file (OS 12587603) as a starting point for most of the flex/ethanol related tables, or scaled some tables in a similar fashion to the Tahoe tune, to hopefully have a reasonable starting point for some of these cranking fuel/after start fuel tables.
I then copied all the changes over to a C5 Z06 file on the same OS. I then converted to EFI Live Custom OS, but that's kinda beyond the scope of this thread.
I did a full-flash on my first flash to a C5 file. I don't think it's required if the OS are the same, but I did anyways just to take any extra guesswork out of it.
You will likely have 3 codes. P0135 and P0155 are for the O2 heater circuits if you didn't ground those to the PCM. P0315 means you need to do a CASE relearn procedure now that you switched to a new PCM.
All said and done, everything appears to be working as advertised. I filled the tank with E85 and then watched the ethanol content click up. As content went up, the target AFR (stoich) was constantly updating as well. I added a generic 2* of timing to the ethanol timing table to test it's functionality, and timing was also slowly increasing at idle with ethanol content (there is a specific PID to monitor timing modifier due to ethanol).
Attached are some starting tune files with Flex Fuel enabled for EFI Live and a config file that defines all the extra flex fuel related tables I was able to uncover. I made copies for both operating systems.
Pretty cool.
Do you need to upgrade the fuel pump for more volume when on E85?
How do you deal with the VIN number? Or is it even necessary?
That's one of the things I wanted to actually go thru the motions and figure out the little nuances before I post up definitely about it. It's my understanding that you will need to copy/paste your VIN to new PCM and perform a PCM/BCM VATS relearn. I've seen the emergency procedure of doing it by leaving the key 'on' engine off for 10 minutes and then turn it off, and repeat 2 more times. With EFILive/hptuners there should be an easy relearn function to simplify that a bit. I have EFI Live so I'll be able to speak to it..... I know changing the VIN is super simple. Worst case several open source options allow VIN change and such now too. I'm not 100 percent certain VIN change is required, but doing this you need some sort of tuning solution, so I don't see why one wouldn't do it anyways.
Fuel pump...... based on my nerdy math, going from E10 to E85 requires about 35% more fuel volume
There's a good injector and fuel pump calc on this page that has BSFC data for E85.... it assumes 40% more fuel required for E85 so it's a little conservative but should work well.
By my calcs 700bhp on pump gas is same fuel flow at 500bhp on E85. So that may be a good measure for what kind of fuel pump you might need for the setup. I'm going to guess that most drop in pumps for these cars would be enough for typical NA E85 build, stock cube etc. I have the C6 style fuel system and the lingenfelter drop in 450 pump so it should be plenty. I guess BAP and vacuum switch on stock pump is another option, but a real E85 rated pump is probably the *best* way to go.
I am running Deka 60 injectors which is a bit overkill, but it's well matched to max out at about the same point as my fuel pump I think and they were cheap, good data available-- so far they've been working really well. Should only be easier once running E85 as pulsewidth will increase quite a bit at idle etc.
Got the car running on the P59 PCM just now. Tune still has flex fuel disabled, I am going to wire up the 3 wires to the sensor, enable it in the tune and then continue testing. Went surprisingly smooth, no drama and fired right up.
- You have to grind down the red plastic connectors. Easy 1 minute job with a dremel.
- P0135 and P0155 are the codes you'll get associated with the heater circuits. I disabled them and everything seems to be working just fine.
- You'll also have a P0315 on startup. You need to do a CASE relearn to clear this one.
- Use PCM terminals like this for adding the various pins https://www.ebay.com/itm/EFI-Connect...-/141623047853
- EFI live has a "VATS relearn" function built into tune tool. I re-linked the PCM and BCM before flashing the PCM with updated tune etc. Just had to command the relink and power cycle.
- I did change my VIN, but it worked fine without changing it. Function within EFILive tune tool again.
- I did a full flash just to be safe, not sure if that's required or not since the OS that it came with and what I was going to were the same (-7603).
- After I get all the basics done I will be updating my OS to 12592425, which is apparently identical to 12587603, other than -2425 was part of the column lock fix recall. Calibration is identical.
OP updated as well. Let me know if you guys have any questions
If someone is able to flash those tunes and then read them on hptuners I can post HPT files as well. I know there's others floating out there as well but kind of an unknown to me what's actually changed in them. Or if someone wants to convert the CAX files to XDF format for hptuners use.
OP updated as well. Let me know if you guys have any questions
If someone is able to flash those tunes and then read them on hptuners I can post HPT files as well. I know there's others floating out there as well but kind of an unknown to me what's actually changed in them. Or if someone wants to convert the CAX files to XDF format for hptuners use.
If I was closer to you then I would pull the hpt file from your car, but alas, ohio and florida are pretty far apart haha
Glad you got it all figured out man. Fuel level gauge works just fine? No TAC module issues at all?
If I was closer to you then I would pull the hpt file from your car, but alas, ohio and florida are pretty far apart haha
Glad you got it all figured out man. Fuel level gauge works just fine? No TAC module issues at all?
Another option would be for me to read it with PCM Hammer and then post the .bin file--then guys could flash it via open source means to enable FF, then go about their tuning per normal that way or hpt or efi.
Fuel gauge works fine...literally not a single issue or weird CEL or light or anything. I also have a late 03, which is C6 style fuel system just like the 04. But in the past on this car I actually flashed back to an older OS so I could play around with some Custom OS stuff with EFLive and everything worked....with the exception of my trans fluid sensor (only thing I noticed anyways).
I think all of the TAC module issues and fuel gauge issues were related to doing a segment swap to get FF working. Using a truck engine calibration segment that didnt support DBW or got confused when with the dual tanks on the C5 etc. When I first did "key on" with the PCM in the car, prior to flashing, I had some DBW/TPS code (it was a 4.8 truck file/PCM). All good once I went to the 04 C5 based file.
It was a lot less drama than I thought it would be, and wish I would have done it a long time ago. There is/was a lot of old or wrong info on the subject, or made it sound like some voodoo magic was required to make it work, which is why I decided to make a little how to thread of sorts.
Been messing around with some phone apps / OBD bluetooth dongle to define and be able to monitor some params without having laptop or EFI flash scan. To include Knock, EGR V (for fuel pressure or wideband AFR). I haven't found the GM specific PID for ethanol content (the generic SAE one doesn't work, probably because this car is old/pre-CAN), but I was able to use "commanded AFR" and rearrange the equation to get real time ethanol content on the phone. Some limiting factor are that i doesn't work when the engine is off (commanded AFR is 0.0 in this case), or during engine warmup when the car is still in open loop. But once you're in closed loop targeting stoich AFR, works fine. It says "fuel level" because I had to pick something out of the drop down list and ethanol content wasn't an option in this particular app.
Man why didn’t you chop through my threads before getting started. There was a much easier route for you.
P01 pcm can support flex fuel tables it’s really a matter of reflash with the correct file settings . You could have avoided all the wiring and pinning bs with it to hook up a ethanol content sensor . I’ve posted it but if you need the number I’ll list it for you . All you is the gm ls3 harness if I recall male end and rig it to power and ground it attaches nicely on the fuel line . I have mine both tuned for flex fuel and run a pro-flex as well . And you can read ethanol content live instead of wondering
Last edited by Speedy007; Jul 7, 2020 at 10:10 PM.
Man why didn’t you chop through my threads before getting started. There was a much easier route for you.
P01 pcm can support flex fuel tables it’s really a matter of reflash with the correct file settings . You could have avoided all the wiring and pinning bs with it to hook up a ethanol content sensor . I’ve posted it but if you need the number I’ll list it for you . All you is the gm ls3 harness if I recall male end and rig it to power and ground it attaches nicely on the fuel line . I have mine both tuned for flex fuel and run a pro-flex as well . And you can read ethanol content live instead of wondering
That thing is a half assed solution. It appears to just intercept the injector signal and increases commanded pulsewidth based on ethanol content. So it accounts for fueling only, no way to adjust timing based on ethanol content-- plus the PCM has a bunch of other tables that vary depending on ethanol content--cranking fuel, after start fuel, transient fueling, commanded AFR in open loop, etc, and it's not always as simple as adding 30% generic across the board or whatever to get the desired effect. Many times for cold temp E85 starting you want a lot of extra fuel because of how hard it is to ignite ethanol when it's cold, so you just want to pump a bunch in.
In the absence of no other solution...ok I guess we would be stuck with that to make life easy going back and forth between pump gas and E85 tune. P01 does support flex fuel, but only a very small number of truck OSs from what I can remember. There's a good thread over on LS1Tech....works for those guys, but no joy for us since none of which are Corvette specific/compatible OSs, so I think you lose DBW functionality and some other stuff. Not really a viable option for street car. So our only savior is that the 04 C5 is a P59, so there we have a FF capable PCM and OS/tune.
It's also.. $900? I paid about $60 for sensor, $40 for the fuel lines and $50 for the PCM.
That rigged fuel line looks like some bs if I would have known your going to do this I had two lines new with the proflex I literally cut in half what the hell am I gonna do with a 14inch fuel rail similar to what you got . Simply use a double end fitting and out the stock braided line on it . It fits cozy
This was before the aftermath of actually getting cleaned up and the fast 103 boosted on .
You could have done all this with your sensor and no pcm swap sorry It was a matter of re adjusting the pcm . You were tight on track when you said there’s limited is for truck flex fuel before the os became to big but then again there’s a slimmer version floating around still . There’s some cool videos out there that also post it up that’s how I came to know it could be done and got it done .
Last edited by Speedy007; Jul 7, 2020 at 11:28 PM.
Do you have a link or part number to that double end fitting coming off the hard line? I tried to find something like that, but came up empty. I'm happy with my end result, but double end fitting -> FF sensor -> 90* line to rail would have been ideal I think.
Auto zone 3/8 i think or 5/16 have to look at what size disconnect tool End I used it’s one of the two double two pack off the shelf fuel line fitting section 5 bucks . Nylon fuel male union is the name your looking for .
Warning the sensor does become a complete pita to get off again with the set up you seen above . Just because a normal fuel disconnect tool no longer fits lol the smaller ones do or you craft one like I had to .
Last edited by Speedy007; Jul 8, 2020 at 12:52 AM.
OK I found the part. Designed to clamp onto a nylon line, like a bigger version of the 1/4" ones you see with water methanol kits it looks like. Meh, I think I'll stick with my setup for now, it works fine.
Pro-flex is supposed to send me out a dual male ended inch roughly durable pice like the one in your link . Thinking of which I need to get back to them .
If u want to pay the shipping cost from Cali to Florida I got you covered.
OK I found the part. Designed to clamp onto a nylon line, like a bigger version of the 1/4" ones you see with water methanol kits it looks like. Meh, I think I'll stick with my setup for now, it works fine.
When I put my subaru back to stock I just used the Dorman fittings shown below and some standard 3/8" rubber fuel line. Worked out great and went together super quick and easy.
If you put the piece I showed u in the spot of your link and used your stock line from one end of your sensor to the hard line out the car it would be almost replicated completely.
Thanks for that link I’m gonna call up that shop and see if can get the fittings.
Last edited by Speedy007; Jul 8, 2020 at 01:10 PM.
When I put my subaru back to stock I just used the Dorman fittings shown below and some standard 3/8" rubber fuel line. Worked out great and went together super quick and easy.
I actually used those first, and then changed to these braided lines...i wasted a lot of time trying to figure it out lol. I felt better using these braided SS lines with less failure points with the lines being right above the headers.
On my Audi I run a FF sensor too and been using those dorman connectors + appropriate rubber hose with oetiker clamps. I bought some pre assembled lines for the FF kit and one of them ended up leaking at the hose clamp, so I've been kinda paranoid about fuel stuff lately. Thankfully on that car, the lines aren't close to any exhaust stuff.
How to: Flex Fuel on C5
