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.

I use to do it all the time when I was a Tech. No biggy. My neck or knees are not good like they were. Freaking sucks. I can't do what I want to.

Sucks getting old :tiphat:

Neat. Those would appear to be the cruise control and clutch pedal switches that I had tested. Never thought about the adjustment for them. The tests I did should have ruled them out as the problem. I've got nothing to lose playing with them some more though. I'll report back with any findings.

You need to fully depress the clutch pedal to make sure it is closing the push pin all the way. If it is a little bit off, It will not make the contact close. Only then will the clutch inhibitor relay work properly if our car even has one. The older Nissans have for years. Fixed a many...

I haven't had time to toy with them yet. The pedal is definitely actuating the switch fully though. Through the tuning software, you can watch the ECU "seeing" that the switch is being triggered open and closed.

The one for the cruise control on my Z needs adjusted. My cruise is hit or miss. Depends on how I bring the clutch pedal back.

I will definitely play with both of the switches.

Thanks a bunch of the feedback guys. Keep it coming please!

Maybe a visual aide can bring this problem back from the dead.

Still the same issues as before. To recap, I've replaced and/or tested the following: new battery, clutch interlock switch, neutral safety switch, wheel lock (non-existent), new starter control relay, starter tested SAT at auto store, and a new start button. I have tried my usual, and back up, key FOB, both in and out of the key slot and with a new battery. All fuses and relays have been good. I replaced the IPDM E/R fuse box with a secondhand replacement with no change, though I cannot guarantee it was in working order before being installed. I've tested bits of wiring looms and ground points as indicated in the diagrams. Everything I have tested has been good with the exception of the 12V leaving the IPDM E/R fuse box to the starter "S" terminal. Obviously if I had that, I wouldn't be here now. I've traced the 12V all the way to the starter control relay in the IPDM E/R fuse box. It would seem the relay is not receiving the control signal to close the relay. Unfortunately, Nissan doesn't want anyone to know what goes on in their magic boxes, so I'm at a loss where I can trace the control signal to. I've broken open the secondhand fuse box for science and it's more of a computer than a fuse box. So theoretically, the control signal could be getting lost absolutely anywhere in the car and with my current equipment, I have no way of tracing it any farther.

I've toyed with the idea of just jumping the starter control relay or even the starter/solenoid itself, but I have a feeling it's going to end up destroying even more if the car starts when the car is under the impression it is not "supposed" to be starting.

Any techie gurus out there know enough about the wiring to help trace where the starter control relay is losing is control control signal, stopping the relay from closing? I'm pretty over replacing every bit of this car one piece at a time at this point. Anyone want a free paperweight in the shape of a car?

I went back to the beginning and re-read everything and I have a few thoughts:

• If you are in the car and don't depress the clutch, press the Start button once.
• Do you hear the steering wheel unlock?
• Does the start button illuminate "Acc" ?

If the steering wheel doesn't unlock, the engine will not start or turnover.


• When troubleshooting unusual problems (like this one!) you can't assume anything. I think you should check for 12v at the "S Connector" wire at the starter and at the IPDM/ER, when someone pushes the start button.

If you want to get the engine to crank over to verify the starter, you could:
• Remove the fuel pump fuse (in IPDM/ER)
• At the starter, disconnect the small wire on the S terminal
• Use a long wire (ideally with a 5-10 amp fuse inline with it) to run from the battery positive terminal and touch the S terminal on the starter.
• Engine should crank only for as long as you are touching the S terminal with 12v.

Thanks for the response.

To address your first thought, no. There is no steering wheel lock at all. Nissan stopped installing them in 2011. I have confirmed that there is no module at all under the steering wheel, the fuse is non-existent in the IPDM E/R fuse box, and the wheel does not lock at all.

For your next thought, the start button works as normal. Both the old and new one. If the clutch pedal is NOT depressed, and the start button pressed once, it turns "acc" on". Press a second time and it shifts to "on". A third press turns the car off. Everything in that respect appears perfectly operational. When the clutch pedal IS depressed, it hops across "acc" for less than a second and stops on "on". This is usually where the starter would be engaged and the engine turns over. But as far as the start button goes, everything tests normal.

I have assumed nothing. You may have misread previous posts. I have tested for the 12V going to the starter "S" terminal at multiple locations. It is GOOD going INTO the starter control relay. I have tested pin 80 LEAVING the IPDM E/R (because I can't test the relay directly while it is installed). No 12V.

I appreciate your input for jumping the starter. But as stated, the starter has been tested and is fully operational. It is just receiving the signal to allow it to turn over. I also stated in my last post I COULD jump the starter, but due to all the electrical fuckery going on in this car, I wouldn't be surprised if more stuff breaks tryign out that test.

Sorry for misunderstanding about the starter wire.
It sounds like the fuses, power and wiring are ok...

Does the BCM code B26E8 still come back after clearing it?
The FSM is states (2016 370z BCS-98) that a B26E8 code will "Inhibit engine cranking"

No problem. There's so much going on in this mess of a starting system. I am constantly second guessing and rechecking everything over and over.

The code does return. FSM says that it is the clutch interlock switch. Unfortunately, I believe this to be one of those very vague codes that could be many different issues. If you trace that schematic, I've traced the 12V from the battery, through the clutch interlock, through the BCM, to the IPDM E/R fuse box, and through the fuse box up until the starter control relay (which is not closing as it is not receiving the necessary signal to close the relay). I believe the code is being thrown because the starter control relay is not receiving the signal to shut. Unfortunately, I have no way of knowing where and why that signal is being lost.

Have you tried to bump start it or with the electrical fuckery going on you don't want to try that?

You have a stumper going on. I have dealt with one like this. It was a burn't connector in the main harness. You will need to trace every wire going to and from the clutch inhibitor switch at the clutch pedal and ohm them out. You can try to jump the switch and see if it will crank that way.

I remember that Quest van well. I was out sick with 104 deg fever back in 1999. When I finally dragged my beat to death butt into work 3 days later that van was sitting in my bay. Service manager said I don't care what you do today, just fix that van. I felt rough. Customers were raising the roof. I brought the burn connector I replaced to him to give to the customer. Electrical gremlins can be tough. Hang in there.

I think the DTC name: "Clutch interlock switch" may be misleading...
What if the ASCD / cruise control clutch cancel switch is sticking for 2.1 seconds???

When you read the DTC detection condition is says:
Detects that ASCD cancel switch is in the ON position for 2 seconds or more while ignition switch and clutch interlock switch are ON.

This is saying the ECM can't verify clutch pedal position, because both clutch pedal switches are ON.

The "ASCD cancel switch" (which is also called the clutch pedal position switch) is on the clutch pedal and is closed when the clutch is fully up. This is the switch that turns off the cruise control when we tap the clutch pedal.

As you know, the other clutch pedal switch is closed when the clutch pedal is fully depressed. This is called the "clutch interlock switch"

To test:
• unplug the ASCD cancel switch (this tells ECU that the clutch pedal is not at the top)
• unplug and short out the clutch interlock connector. This tells the BCM that the clutch pedal is at the floor.
• make sure the car is in neutral and/or press the clutch down
• try to start the car.

I had a similar issue on a Mazda 3 and the fix was to replace the switch... What was VERY interesting is that the switch was made by Nissan!

I don't know if I mentioned it before, but I've done that test as well. I hit the start button without touching the clutch to turn "acc" power on which will wake up all the computers and let them know it's go time. I then unplug the cruise control switch and left it to simulate the clutch pedal leaving breaking the circuit. And finally, I unplugged the clutch interlock switch and jumped it. No change. I then used the start button to cycle power a few times as I heard rumors of there being a time limit between all of the switches opening and closing. Still nothing.

Crap!! I was hoping for better news.

The next step is to view what the BCM "sees" for the clutch pedal position.
Luckily, this doesn't require a Consult III+, but just a a cheap OBD scanner ($20), OBD Fusion ($7-14) and their $14 OEM Diagnostic add on.

With this app, you can connect to the BCM and view the clutch pedal switch status. You have checked the switches, BUT that doesn't mean the BCM sees the required criteria to crank/start the engine.

Here is a screen shot from my G37 Sport (6 speed manual) with the clutch pedal on the floor and fully released.

http://www.the370z.com/attachment.ph...1&d=1620773979

Any interest in pursuing this?

I need to check my setup up to see about the cruise control, but I have done that test with the clutch interlock. Using a laptop and the tuning software, I can watch the clutch switch being toggled in real time. So as far as the clutch interlock is concerned, the ECU and BCM both see that the switch is working as intended, which is part of my previous thoughts about the DTC being thrown actually being a generic error.

I'll report back when I check out the cruise control switch through OBD. I don't know if the app I'm using or the tuning software I have tracks that. If not, I'll look into the app that you have.

Well, car is still an expensive but useless hunk of metal and plastic.

Verified that the both clutch switches (interlock and cruise control) toggle as expected through tuning software.

Also verified that the U1000 and B26E8 codes keep returning after resetting ECU while I was in there.

I tried different variations of unplugging the cruise control switch and jumping the clutch interlock. No change as expected.

The HVAC U1000 CAN Bus code shouldn't prevent the car from being started, worst case no A/C.

What is your next step?

At this point, probably sell the car for scrap metal.

I do have suspicion that the BCM is at fault. But not only do I not wish to pay for a new one, I would have to take the whole car to Nissan (three hours away) to have the new BCM rekeyed or to get a new sets of FOBs to match the new BCM. The only logical thing I can think of is the tuning upset something inside of the BCM which is causing the BCM to stick in a "no start" condition, though nothing about this problem has been logical so far.

Ha. Even according to the actual Nissan techs, there is "nothing wrong" with the car. They used their fancy pants Nissan only computers and allegedly there is nothing wrong with any part of the car. It just doesn't turn over. Because that makes sense. They offered to start swapping out the car piece by piece starting with the IPDM for a low cost of $2.2k for the fuse box alone, not including labor, diagnostics, etc. Instead, they spliced into the IPDM to bypass the entirety of the start circuit using a toggle switch. So you can start the car and it seems to run (mostly, see below) fine now. I have since ordered another IPDM (this is the third one, including the original) and again, no change. The only thing left is to literally swap every single computer (ECO, BCM, FOBs, FOB receptacle, etc.) at once to ensure all the IDs and everything match and that still may not even fix the problem. Also after receiving the car from Nissan, the gear indicator on the dash no longer works and you can no longer turn on sport mode/rev matching. Again, no trouble codes, no blown fuse, no anything "wrong" or "broken" with the car according to me or Nissan. I am beyond over this car.

Go back to the stock tune.

Done. Multiple times. No change. Different ECUs, stock and new tune. No change.