[DonMaximo]

I have (what I think) is a unique situation.

Several months back, I had a problem with a 1-year old NSS. I pulled the 2 connectors out, placed a jumper in both, and the car started. Of course, it started without having to depress the clutch.
Not an ideal situation, but low on the priority list as this is 2nd vehicle and used only on weekends and I'm the sole driver.

I recently learned (or assumed) that Deceleration Fuel Shut Off (DFSO) mode uses NSS signal to determine when engine will be separated from driveline and as such, fuel shutoff algorithms kick in. In short, "if" I want to continue refining my tune, I need to address this NSS.

I removed the existing NSS, bench tested it, and it was fine. Since I had a new one, I carefully installed it.
Voila ! It worked. Car would not start until the clutch was depressed. I go to bed a happy guy.

30 minutes ago I go into the garage to fire her up.... Nothing !!
I've got a loud horn & lights and the battery has 12.5 volts (handheld volt meter).
I put the battery on tender anyway.

** I have little doubt that the last change made to the car (ie. NSS) is the root cause.

I'm trolling for what could be causing this latent/delayed failure ?

FYI- I have a TKO600 transmission.

Whatever the issue is --- it has occurred for 2 different NSS's, both of which new or less than 2 years old and pass Bench testing. I believe the issue is something other than the switch itself.

I'm going to wait on replies... but if nothing substantial comes through, I'll disconnect battery and see if that provides a different symptom and for how long.

Any ideas would be greatly appreciated.

[cgrey8]

When you say it doesn't crank, do you mean the signal never gets to the starter to turn over the engine? Or is the engine spinning, just no crank?

If the engine is turning over, just not cranking up then datalog the crank and see if the EEC is firing the injectors, or responds in any way to the crank.

[DonMaximo]

Thanks for responding Chris...

After I push tune to EEC -and- prior to starting, I put ignition key in ON position until I see WB gauge/indicator light show that sensor is at operating temperature.

When I turned key to start... not a sound came from the car. Basically, the same behavior you would have if you tried to start a manual vehicle when the clutch is not depressed. Nothing.

I'm fairly confident that if I put the 2 jumpers back into the 2 connectors at the NSS, the car will fire right up.

I just updated my post to include the fact that I'm using a TKO600. This however, would not explain why everything was fine last night... and not this afternoon. I had considered that by somehow reconnecting the plugs into the NSS, that I may have introduced a short-circuit, hence the battery, horn, and light test. Battery measured at 12.5 volts, so I should have got something...even a clicking solenoid perhaps. Nothing !

[cgrey8]

If you did create a short, then you probably burned the NSS out. Check it. If it is now bad, then yeah you got some scenario where you are shorting it out.

[DonMaximo]

As an aside... is my assumption regarding DFSO correct ?

Is a properly operating NSS necessary for DFSO (or other) tuning when using a manual transmission ?
I was reading through various posts and this subject caught my attention.

I never considered it earlier as my datalogs captured TRANSGEAR changes, 0-5.

[decipha]

you can set dfso anyway you want, the nds doesn't make a difference

sounds like you got a wiring issue