2017 L86/8L90 Start/stall issues

[aj89]

I am new tuner, I am building a 67' C10 and purchased a 2017 L86/8L90 combo, after installing the powertrain and hooking up to HP tuners I have found that the PCM I recieved with this assembly is from a 2018 5.3. I have deleted VATS (did a write entire) and a couple other minor things. The engine fires and shuts down shortly after (1-2 seconds). I am not using the FPCM, I have a Walboro Pump and Corvette Regulator. After doing some reading on this forum I downloaded a stock L86 tune from the repository and copied the tables over and am having the same issues. I am not looking for anything fancy at this point, just looking for something to be a daily driver. Can someone help me out? I have attached the latest 5.3 tune I have done and the second has the same parameters with the tune from the repository.

Current Faults are:

P0073 - Ambient Air Temp Sensor Circuit High
P0113 - Intake Air Temp Sensor 1 Circuit High
P018C - Fuel Pressure Sensor B Circuit Low
P0532 - AC Refrigerant Pressure Sensor A Circuit Low
P057C - Brake Pedal Position Sensor Circuit Low
P0645 - AC Clutch Relay Control Circuit

Thanks in advance

08 - 2018 5.3 SPEED LIMITER DELETE.hpt
TEST.hpt

[K-fed]

Did you disable starter and clutch tables

[aj89]

Here is what i have so far:
- under the OS tab I have the "VATS Patch 1" set to DISABLED
- under System - General - Starter Relay - Starter Diag is set to DISABLED
- under transmission - manual - clutch position sensor - Clutch Interlock is set to DISABLED

Thanks in advance

[K-fed]

Fuel pressure is set to 72psi? Also make sure the wires your pulling power from on the 67' to the standalone harness have constant power to them after cranking. I had a friend with a pickup that year with a similiar issue and he found out after his would fire the voltage would drop from a supply wire wherever he was pulling it from.

[aj89]

I triple checked the fuel pressure, all is well. The wiring is good. I verified both of these by borrowing a 2014 PCM from a buddies project and it fired up first time and idled. It has to be something in the parameters of this 2018 PCM. Hoping someone can point me in the right direction.

[Shrek]

... borrowing a 2014 PCM from a buddies project and it fired up first time and idled...

This is indicative of an issue (or mismatch) with your wiring harness.

The 2014 to 2016 models used a 4-wire Fuel Rail Pressure Sensor.

The 2017+ models used a 3-wire Fuel Rail Pressure Sensor.

The ECM is pinned differently with respect to a 4-wire Fuel Rail Pressure Sensor versus the later 3-wire Fuel Rail Pressure Sensor.

Where is your wiring harness from ?

[aj89]

I purchased my Harness from Swap Specialties. I have the 3 wire Rail Pressure Sensor, indicating a 2017+ model as Shrek listed above. I checked my wiring from PCM to Rail Pressure Sensor against the wiring diagrams I could locate online (L83 not L86) so i am hoping someone with a little more experience with these Gen V's can check my work.

PCM Blue Connector PIN 41 (BL/WH) goes to Rail Pressure Sensor (BL/WH)
PCM Black Connector PIN 3 (BK/GN) goes to Rail Pressure Sensor (BK/GN)
PCM Black Connector Pin 16 (BN) DOES NOT go to Rail Pressure Sensor (BN/RD) Pin 18 does. (From the diagrams I can find it shows that PIN 16 was the 5V reference for the 2014-2016 models)

I have not chased down where Pin 16 BN wire goes at this point. I am hoping a more seasoned veteran can check this info out for me and confirm my findings before i go chasing wiring and re-pinning PCM connectors.

Thanks in advance

[aj89]

I just found a few more diagrams that state the PCM Black connector Pin 18 IS the correct pin for the Rail Pressure Sensor 5V reference. Which makes sense because I don`t have any codes to do with the rail pressure sensor. With the 2014 PCM Installed i did have rail pressure codes active when running but i didn`t pay any attention to them as I knew the rail pressure sensors were different between model years.

[aj89]

For what it's worth here is the log file for two start up attempts. Both fire for a second then stall out. 21-11-02 12-24-02.hpl
I am heading back to work tomorrow for two weeks and will be unable to test or pull information from the Truck during this time. If there is anything else I can provide please let me know.


Thank you

[msbweiland]

Take a look at your pcm pin outs for the sensors and double check your harness. I bought a ?complete? setup from a vender and they gave me a 2016 harness and 2017 engine and pcm. Both had the same fuel sensor, but the pin out for the sensor return was incorrect at the pcm. Took me forever to find. I had to get diagrams for both years and take the time to check the connectors at the pcm.

[JKLTGuy]

There is a pile of differences in I/O assignments from 2018 to 2017. If the harness is for a 2017 engine then I suggest you get your hands on a 2017 PCM/ECU. I found out the hard way installing a 2016 harness and 2016 L83 in my Jeep with an E92 2017 PCM. Pop, bangs and just would not run - all kinds of issues. Changed to a 2016 PCM and away it went like it just came from the factory.

[aj89]

I understand the issues using the 2017 PCM with the 2016 harness as there are some major differences. The diagrams I can find online everything looks the same 2017-2018. Continuing on checking the pinouts as MSB suggested above, everything seems to be checking out at this point. Does anyone out there have another test/check i can perform? The nearest Gen V tuner is 3+ hours away, the plan was to take the truck down there when complete for fine tuning, but would hate to make the trip just for something stupid to get the thing running in the shop. I've seen posts of people talking about other parameters that needed to be changed when performing the vats delete. I have reached out to that person via PM but no response. It seems that as soon as the ITV begins to open is when the engine dies.

[aj89]

Update: It runs, can't say for certain what exactly it was. Only thing i can figure is i had a connector that wasn't tight. After pinning out just about everything i could think that would cause this condition, i tried to fire it up and away she went. Thanks to everyone that lent out their opinions. I've attached the file of it running for anyone that is interested.

21-11-25 14-18-24.hpl