What I Have:
2015 Corvette Stingray 1lt with DSX low side fuel system, alky meth kit, procharger kit, e85 sensor, and built motor.

Current Situation:
We found the driver's side upstream O2 sensor wire melted and all four wires touching after removing the whole harness and inspecting all the wires. We repaired the short, reloomed the harness and reinstalled it into the car. With the stock tune it cranks but does not start. With the e85 base tune from our tuner, it slow cranks/doesn't crank at all. Fuel rail pressure is logged at 80psi and low side pressure at 57 psi.

Car powers up normally, fuel pump primes, start button light is green, the center dash and gauges light up and work, I get an error light for ABS and stabilitrak and a reduced engine power message on the center dash, the gear indicator flashes 7 a few times and goes away, when I depress the clutch and brake and press the button the car flashes back to the first powered on state described from above. After trying for two or three times the start button goes amber, only the center dash and radio comes on with the sides gauges not working and when you depress the clutch and brake and press the button nothing happens and fuel pump doesn't prime.

Codes:
P0697
P00C6 (After cranking the motor)

Past Codes:
(relevant)
p18c5
p18c7
p0651
(probably not relevant)
p0056
p0057
p0097
p0158
p0697

Background:
Just had an engine out and in service performed by a shop, procharger kit installed, DSX low side fuel system installed, and a triple disk clutch installed.

What we have tried:
Tested all fuses and relays, all working
Move front drivers side engine ground to the front of the motor and make sure it was seated correctly, fixed issue of fuel pump not even priming from before
Replaced battery with a new battery, no change
Disabled clutch safety switch, engine cranks over halfway then stopped, could not replicate
Fully rewritten both the CCM and ECM with HP Tuners, no change
Checking the GAP, gear absolute positon, sensor plug for the correct voltage, I believe I'm expecting 5v, found 5v on pin one and two
Ordered new GAP sensor based on code thrown by ECM, did not fix the issue
Attempted to inspect the rear black plastic part of the wiring harness behind the heads above the bell houses, seems to be no pinch on the harness.
Removed harness after suspecting a short in 5v ref 2 & 3
Found short between all four wires of driverside upstream O2 sensor plug. Repaired.
Inspected the whole harness by removing all looming and looking over all the wires, found nothing, reloomed after the above fix was made.
Reinstalled harness in the car, attempted to start with the E85 base tune, car slow cranks or flashes on start button push like before.
Flashed back to stock Z51 manual tune on my non-Z51 car, press start button and it cranks but no start
Removed HPFP, checked plugger travel, confirmed it was correct.
Cranked over several times to make sure there was no air in the lines, no start
Ordered a new ECM based on the theory the 12v O2 sensor heater wire overvolted the 5v bus on the ECM, testing 08/12/19
Ordered a new LT1 HPFP to swap out with the LT4 HPFP currently installed to check to see if the HPFP is the issue, testing 08/13/19

Other Notes:
Car started and drove on the dyno for 6 hours before the engine out and in service. Shop says the engine was started after it was put back in and ran for 30 minutes with the tachometer going from 0-1000 and idling rough. No evidence of melted grounds or wires in the engine bay has been found yet.

Any advice or explanations is greatly appreciated!
Thank you!

 

Have you checked all ground connections? You said you moved one, I would go back and look at that one again. Other than that you sound like you’re doing a good job of trouble shooting.

Good luck. Trouble shooting weird problems like that can be quite frustrating.

 

I would start by checking the four 5V references produced by the ECM.

 

We ended up pulling the harness out and completely disassembling it. Turns out there was a short on the upstream O2 sensor wire, all four wires had melted through and shorted on each other. After repairing that spot in the harness we continued to look for other harness damage and found nothing. We reloomed and reinstalled the harness and went for another test start. Flashing the car back to a stock tune we managed to get it cranking through the start button but not starting. Code P0697 returned and code P00C6 showed up after cranking. Checking the logs we found that the fuel rail pressure was reporting back only 80 psi of pressure. We think either the HPFP is dead, its a brand new LT4 pump, or the ECM's 5V bus got overvolted from the 12v O2 sensor heater jumping into the O2 sensor signal wiring causing the ECM to have an internal 5V sending issue. We measured 1.5v at the MAP sensor which is on 5v reference 3 which seems to back up this theory. We also did measure a 55ohm resistance on pin 1 and 3 of the sensor plug. The MAF is also on that rail and it seems to be working fine in the logs. Another fact to back up the theory of the ECM overvolting is that fact that when we went to crank with the e85 base tune provided by our tuner, the car would slow crank or not crank at all but when switching back to the stock tune it cranks just fine. We plan on replacing the ECM tomorrow night to see if that fixes our issues. If you develop any theories of your own from this please let them be known, the desperation will be setting in for sure if the ECM swap doesn't work. Thank you!

 

Did you ever figure this out? I’m having the same issue

 

Did you ever figure this problem out? I seem to be having the same issue

 

Any update on this?

 

[QUOTE=adam8121;1601688533]


Any update on this?