Car will not start after tuning
 

Greeting Pals,

Recently tuned the Z with a custom tune (remote tune). Car was in the garage. I started it up and drove it out to the yard so I could sit in the sun while I got the ECU flashed. Tuning process was superb and tune was flashed onto the ECU with no issue. All was right in the world until I went to start the car and get ready for some data logging fun. But alas, car did not start. Did not even try to turn over. Nothing. Welp, that's no good. Contacted tuner and we went over some troubleshooting. We went back and forth between custom tune, original OEM tune, older version OEM tune, and custom tune with NATS disabled. No change. Every time the start button is pressed, car will flip past "acc" to "on" as normal. But starter doesn't crank. Car just remains in "on". So tune doesn't seem to be the issue. Below are more troubleshooting steps I've taken with no joy:

1. Battery in FOB was fine, but replaced anyways. Tried starting with FOB in and out of the key port. No luck.
2. Car battery was on a tender the whole time during the tuning process. Voltage was fine with and without tender. Replaced battery anyways. I also left the battery disconnected a few times, including overnight, in case a relay or something was hung up. No luck.
3. Looked into the wheel lock problem that was a big deal with the older 370s. I have a '13 NISMO. They apparently stopped putting the ESCL modules in the cars around '11. Verified the module was not under the steering column. Verified the fuse was non-existent in the IPDM E/R fuse box. No luck.
4. Toyed with the clutch interlock switch (neutral safety switch). Tested the switch with a meter; open when disengaged and nearly no resistance when engaged. Test SAT. Looked at the switch in the tuning software. It toggles open and closed appropriately according to ECU. For science, I also tried starting the car with the switch disconnected and the harness side connector shorted out. I also tried combinations of the switch used normally and the switch shorted while disconnecting the cruise control switch at the top of the clutch. More than enough evidence that both switches appears operational. No luck.
5. Verified that the starter control relay was good with a meter. Relay audibly closes when start button is pressed. For science, I replaced the starter control relay. No luck.
6. Used a meter and tested every single fuse and relay I could get my hands on. Not a single component was faulty.
7. Tuner was kind enough to send me another ECU even though mine shows no signs of not being operational. New ECU, same issue. No luck.
8. Followed the FSM flow chart for failure to start. All tests were SAT (even with old battery). Resorted to the tried and true method of giving the starter a few wallops in the event that it was seized up. No go. Removed the starter and took to auto parts store for testing. All tests SAT. No luck.

I'm at a loss about what else I can try. If I follow the the system diagram for the starting system, I have have eliminated all but two (really three) options:

1. The starter relay, not to be confused with the starter control relay, appears to be integrated into the IPDM E/R fuse box. That would be a real drag to swap out that whole thing. But options are running thin.
2. The BCM. Apparently it's in the cabin next to the fuse panel under the driver's side kick plate. Also lame if I need to start toying with that thing.
3. After those two options, the entirety of the start system will allegedly be tested/fixed/replaced. Although highly unlikely, the wiring harness itself may somehow just gave up on life.

After tuning these are the DTCs that I have been able to pull:

1. Using the tuning app/OBD dongle, I have a HVAC2 "U1000-00" (appears to be CAN lost communication) code after flashing ECU. Code returns after clearing.
2. Using the tuning app/ OBD dongle, I have a BCM "B26E8-00" (appears to be clutch interlock switch) code after flashing ECU. Code can be cleared and stays cleared.
3. Using a generic app/different OBD dongle, I have a permanent U1024 (also appears to be CAN comm circuit/VVEL related) code after flashing the ECU. Permanent code cannot be cleared.

Although it does point at a generic wiring harness fault, I don't believe that the harness suddenly got disconnected and/or broken somewhere at precisely the same time I first flashed the ECU. If that was the case, it would also be unlikely that I could continue with more flashes and complete all the tests I have with no errors or more DTCs.

So that's where I am with my very fancy and very expensive paperweight. I was hoping that one of you might be able to chime in with something that I may have tested wrong or another component that may be at fault. I will totally bribe anyone that can help me find a solution for this car with a burrito. Thanks in advance for anyone that can provide any advice or insight.

Who's doing the remote tuning?

I had refrained from saying before on purpose. I'm not looking to point any fingers. I will say that the tuner has been very helpful with trying to find the issue. Seems to be a problem that they have never ran into before though. Until the actual issue is found, it's hard to even say if it tune related or a freak occurrence at the most inconvenient time imaginable.

Does the engine fire up when push started?

Excellent troubleshooting! What an unusual issue.

UpRev or EcuTek?
What is your ECUID?
Did the replacement ECU have the stock programming?

I have seen that in some cases when the ECU is very busy (like uploading a tune) it can create false CAN bus faults. This is because the ECU doesn't have the time to send the normal "heart beats" to the various modules. These are resolved once the ECU is back to normal operation and the vehicle is driven a few times (drive cycles) BUT you can't do that...

If the starter relay is being activated, it isn't a NATS issue...
I assume the "red key" dash light is not on. (verifing it isn't a NATS issue)

I have seen a few cases where the starter wire connection is corroded (between copper lug and copper washers) and it arcs when starting, creating a poor electrical connection. 80 grit sandpaper fixes it.

I know you had the starter tested, but have you tested for 12v at the thin starter cable when someone pushes the start button and do you have a constant 12 volts at the thick starter cable?

Also, look into the B26E8 / clutch interlock switch - that might stop the car from starting if it thinks the clutch is not pressed.
I think you can use a wire and jump the 2 connections in the clutch switch connector to ensure the BCM thinks the clutch is pressed.

Good luck!

Did try to push start it with some pals. Couldn't get enough of a run to start it. Hard to say whether it would have been effective if the car had been able to be pushed faster. As the test was unreliable, I hadn't included it in the original post.

Thanks for the advice.
If it's what I think it is, ECUID appears to be 3GY2D. Also flashed 3GY2B. The replacement ECU was pre-flashed with the custom tune.
The tuner also agreed that the DTCs likely weren't a big deal.
I can also confirm that I have gotten no red key lights.
I did clean the starter when it was out. Normal grim was as expected. Electrical connection was flawless though. Gave it a dab of dielectric grease before putting it back in.
I have confirmed that the normal voltages and voltage drops are present at the cable going to the starter as listed in the FSM. I haven't been able to test the smaller cable going to the solenoid on the starter yet. My guess that with a operational starter and 12V at the starter, there's going to be no signal at the smaller cable or the car would be turning over. I will report findings though.
The clutch interlock was what I had tested as noted above, including shorting out the connector. I appears that I was a incorrect and also referring to it as the neutral safety switch. It appears that the neutral safety switch is at the rear of the trans and seems simple enough to check even though it is not listed as part of the start circuit. I'll be giving that a test along with the smaller starter control cable later today.

I won't place any blame but I still want to know the tuner lol. Unfortunately, I also understand there are social media platforms where any negative information (whether true or not) impacts business and reputation.

GL on the repairs

You need to know if it will start by jump start. Can you get a friend with a pickup that can pull you, drive at about 20 mph and then you dump the clutch in 2nd gear?

Back when I worked for a living, when something started malfunctioning after being worked on, we always started with the things that had changed during the repairs. You say you worked on the starter motor and wiring - I'd start there and double-/triple-check everything.

Random but have you checked the limiter switches on the clutch pedal?

Forgot to post my promised update.

Gave the the neutral safety switch a test even though it should have nothing to do with starting the car. Switch tested SAT.
I tested for the 12V signal going to the smaller start control cable that tells it when to turn over. As expected, no go. Tested the run from the starter connector back to the IPDM E/R fuse box as well. All good there so that part of the wiring didn't magically break.

I have a secondhand fuse box on the way to give that a try. If that's not it, it's down to the BCM and the wire loom.

I don't know anything about them. Care to educate me?

There's 2 of them. If they're out of adjustment, the car won't start. Sometimes the lock nuts come loose.

Yeap, mine is out of adjustment a touch. Every now and then I will get a no start. I just slam the clutch pedal down and it does the trick for now. My neck is giving me chit and I can't get under their to check the adjustment.

It's a b1tch getting down there and even getting a wrench on the locknuts.