While my car was fully built and I have no more parts, there were several issues I had to address to truly complete the car.
Everyone will have a different experience...this was mine. Kit car life...
Front Lift - beeps, but no lift
I should have addressed this earlier in the build, but I assumed I had a simple wiring issue I could resolve later.
After verifying the wiring was correct and I had good grounds, I tested fuses 13Q and 13X (back of panel) and both had power.
I then unplugged the pump (connection near the pump) and tested the pins...no power.
This told me that the pump controller has an issue (e.g. bad relay). I contacted Ultima they sent a new controller.
I plugged it in and it still didn't work. WTH? After closer inspection, one of the pins in the plug was seated too low.
I took apart the plug, reseated it properly, put it back together and it worked!
ECU - no power
When I went to attempt the first start, the AIM computer started up, but fuel pressure read 0 psi. I also noticed I didn't hear the fuel pump kick on.
After verifying multiple wiring connections, I got to fuse 13R and confirmed 12V was coming out the back. This connects to Wiring Loom #85 (ECU Interface). I traced the wire to #85 which was fortunately easily accessible when I removed the stereo. I tested the wire...no power??? How is that possible? That wire goes from the fuse panel, through the harness trunk to the center of dash...a very short run with no risk of getting cut. I believe the wire was defective since this also happened to Ahmed (thanks, Ahmed, for pointing in this direction).
I temporarily used the radio loom wire since it was also key on power...it worked! Fuel pump turned on. ECU got power. I then ran a new wire from the fuse panel to #85.
Steering Wheel Fans Button - nothing happens
All of the buttons on the Raptor worked except the fans. The fans did turn on automatically at 192 degrees, so I knew they were good.
I asked Ultima about it and after a little back and forth, it was determined the power wires weren't fully connected in the loom.
Easy fix: splice in the Raptor plug orange/black wire to either fan orange/black wire. I did that and it works now.
Exhaust - doesn't fit right
Every car/frame is slightly different and every fabricated part is slightly different.
On the LT4 (and LT5), you want to mount the muffler or x-pipe as far back on the frame as you can.
When you install the cats, there is a small margin for adjustment with the olives and clamps.
Unfortunately, the cats I received were too long and pushed the x-pipe back a 1/2".
This caused multiple issues:
1) The rubber bobbins were forced on a 45 degree angle and would certainly break one day.
2) The clearance for the remainder of the exhaust got too tight (was then touching frame)
3) The exhaust pushed back too far and opening/closing the rear clam interfered with the mesh.
I contacted Ultima and they were happy to fabricate new ones for me.
I sent them measurements and 4 weeks later I had new, shorter ceramic coated cats that fit perfectly.
Rear Clam - multiple issues
1. The left NACA duct was hitting the left cat. I had to remove the cat, clean out the copper gasket and reinstall it twisted down as far as it could go.
This gave me a 1/2" clearance between the cat and the body. I wanted to raise the back of the rear clam up, but unfortunately the trans mount bolt is already touching the bottom of the clam. I need to find a solution. I might change the bolt to one with a smaller head (e.g. from hex to round).
Pedal/Throttle - pressing pedal does nothing
This one was the biggest pain! Huge thanks to Shaun for helping me diagnose it.
This took a few weeks to resolve as I kept getting new clues that pointed to new ideas to resolve coupled with wait time for new parts.
- Purchased a reputable tuning tool on Amazon. Waited a few days and it didn't work.
- Spoke with Ultima and they said they really can't help with engine issues. They told me to contact a tuner. :(
- I already owned a FIXD wireless code reader and read the ECU. It returned 4 codes
- P0131 - O2 Sensor related. Not an issue as post-cat O2 sensors are not required or installed.
- P0443 & P0458 - Evap related. Not an issue as we deleted that sensor and clocked it off.
- P16E5 - No description.
- I also used the FIXD tool to get live data reading of the pedal (position D & E) and the throttle. When I pressed the pedal, the data changed. When the car started and ran for a few min, I could see the throttle data change. This told me both were wired properly, but not working together.
- I researched P16E5 and it pointed to fuel sensor...more specifically the fuel rail (high) sensor.
- I reached out to Ultima and they again said a tuner needs to help me. They recommended a new Ultima customer named Ben.
- I contacted Ben and he recommended I buy an HP Tuners tool. I ordered one and it came a few days later.
- I scanned the engine off and while running and noticed the fuel rail pressure was 95,000!?! This is the problem. Bad sensor?
- I then chatted with Shaun (we've been chatting a lot as the first 2 people to build LT4 RS's in the US) who did some research and informed me that the LT4 fuel sensors changed in 2021. Pre-2021 were 4-pin analog, while 2021+ are 3-pin digital. I verified the everything was 3-pin. We discussed and thought maybe the wrong ECU was shipped to me or maybe the ECU wasn't programmed properly (there was a programming sticker on top of another sticker on the ECU). GM ECUs are often re-flashed for new cars. Mine was.
- Now I need to become and expert on GM 3-pin vs 4-pin. I did some research and found the ECU model/code changed from E92 to E92A in 2021. I pulled out the HP Tuners, scanned the computer and found E92. That's it! (so I thought) - I have the wrong ECU. The fuel rail must be sending a digital value, but the ECU is expecting an analog value. And since the value is insanely high, the engine won't rev in order to protect itself.
- I then contacted GM as it appears I might have the wrong ECU or a faulty fuel rail pressure sensor. They asked me to check the voltage on the fuel sensor (low) first...5V...perfect. I also knew this sensor was good as it was reading 75 psi (perfect) and I also had an AIM (dash computer) sensor installed that was also reading 75 psi. GM then said I need to take it to a GM dealership to get diagnosed and fixed. Only problem: I can't drive the car. Fortunately we have AAA and they'll tow from my driveway to the dealership.
- The next day I called AAA and a truck came out. They said no way they could tow it. Too low. Note: The front lift wasn't fixed yet so it sat 3" from the ground. This turned out to be a good thing.
- That night, I ordered a new fuel rail sensor. It will take 3 days to arrive and I'll try it later. While I waited, Shaun said "I wonder if the issue is in the ECU harness. Maybe it was wired for 4-pin even though it has 3-pin connections." Sounds strange, but who knows. I opened a Support Ticket with Current Performance in FL (they built my ECU harness for Ultima). They responded in less than 30 min and confirmed the wiring diagram from Ultima (which they build the harnesses off of) was wrong and built for 4-pin. Easy fix: "Move the wire from pin 19 in Black (J2) to pin 41 in Blue (J1). You have to cut and lengthen the wire to get it there." These wires have special connections and they mailed me one. It took a full week to arrive (thanks, USPS). I installed it and everything worked! Engine revs, fuel pressure fluctuates between 1,000 psi and 3,000 psi based on throttle, and fault code is gone.
No more issues. Time for a drive!!!