Flex sensor stuck at 40% and fuel pressure reading zero

[lynmup]

Pulled my factory line to install a new -8AN line to the HPFP. The last flex sensor I installed was with a compresison fitting so could not get it unmated to the stock line so I bought a new one. Once I installed the new flex sensor with the Snow Performance manifold along with the new fuel pressure sensor adapter, I started the Yukon and I see 40% alcohol when I had 80% proior to parking it. Also noticed there was no Flex fuel advance or retard in the timing. Also the fuel pressure is reading zero which is wrong as I was driving and could even go WOT with plenty of fuel on tap.

I ran out the full tank of E85 and put in non ethenol 91 octane and it still read 40% so I turned off the flex fuel in the tune and it drove much better. Maybe a bad sensor so I bought a new fuel presure sensor from GM and same issue, reads zero. Both being bad must be wiring but nothing was touched.

I did pull the heads due to cracks on the common wall but the wiring on the drivers side coil mounts was also untouched. Even went as far as puling the insulation off wire harness to the ECM that was around the turbo cold side and it was fine so I re-routed it for better clearance.

Anyone have any possible idea where to look or had experince with this exact thing as I am clueless. I could find the ground on the pin and install a new wire but I find it odd that both are doing the same thing. Visual check foundnothing obvious but something is disconnected somewhere.

Added a pic of the manifold where I removed the sensor to entirely eliminate it. Everything is in the same location so wiring or original orientation did not change.

[lynmup]

Anyone?

[enmanuelpimentell]

You are logging an incorrect channel for the flex fuel, the right one is called "ethanol fuel %". If you are talking about the low side fuel pressure sensor, i don't know where is it located but I had 4 clients with gen 6 zl1 and all of them in one point had to replace that sensor. I don't have your current tune but if you if you want to add or retard timing you have to modify the flex fuel timing table, as well as enable the flex fuel option. Post your current tune and log so we can help you further.

[lynmup]

You are logging an incorrect channel for the flex fuel, the right one is called "ethanol fuel %". If you are talking about the low side fuel pressure sensor, i don't know where is it located but I had 4 clients with gen 6 zl1 and all of them in one point had to replace that sensor. I don't have your current tune but if you if you want to add or retard timing you have to modify the flex fuel timing table, as well as enable the flex fuel option. Post your current tune and log so we can help you further.

Thank you for the reply but before pulling the heads it was working flawlessly. I think I may have figured it out as I put a spacer in between the harness on the firewall and believ that may have pinched a wire, going to take it apart and verify this afternoon.

[lynmup]

***Update***

I removed the tank and swapped out the Walbro 525 with a 450 and also replaced the flex sensor, the fuel pressure sensor on the fuel line and the fuel pressure sensor on the tank and still the same issue. No idea why the Alcohol is reading 40% while only running 10% 93 octane and also why the demanded fuel pressure reads zero when it was reading the actual pressure previously before parking it to remove the heads. The wiring from the fuel system travels down the frame under the driver fender and to the fuse block. Nothing was ever touched with this harness so I cannot for the life of me, find out why this is happening. Anyone able to provide a solution at all? Could this be a bad FCM or a ground? I repositioned the ground wire behind the front driver tire and also cleaned the frame to make a better contact and still the same same issue.

Please someone point me to where I need to go to fix this.

First screen shot is a log I did prior to parking, Was not logging the requested fuel pressure at that time. Second screen shot is what is occuring now. All that was done is the flex fuel manifold, nothing changed wiring wise.

[lynmup]

The flex sensor and Fuel pressure sensor issue still exists however, getting rid of the Walbro 525 and swapping in a Walbro 450 pump seemed to get it running right. The pump I installed in November was bad the entire time...who would have known.

[enmanuelpimentell]

The flex sensor and Fuel pressure sensor issue still exists however, getting rid of the Walbro 525 and swapping in a Walbro 450 pump seemed to get it running right. The pump I installed in November was bad the entire time...who would have known.

Brother. you have to log a parameter that is is called "ethanol fuel%" instead of alcohol

[lynmup]

Brother. you have to log a parameter that is is called "ethanol fuel%" instead of alcohol

I don't think you guys are understanding... all was working perfectly fine when I parked it. Now, after putting the heads back on, this is happening. The log or channel configuration isn't the issue, it's the ground to the sensors or that circuit. I just cannot find it.

[lynmup]

Did some voltage checks on the Flex sensor pin and no voltage so thinking the Fuel Contorl Module possible died. Time for a returnless...any write-ups on installing one of these on a 2016 platform? Seen several posts talking aout installing but none telling you how to delete the FCM. Thinking about modifying my bucket to hold 2 Walbro 450 umps and set them to a return style and forget it. What to do to disable the FCM so I dont get any codes or anyhing funky as such?

[lynmup]

This issue is fixed! Took it to a Chevy dealership as I thought the FCM was bad, turns out the connectors are exactly the same and I did not pay attention to the orientation when I removed them, they were installed backwards. All that was needed was the connectors to be swapped. Who knew??