Intermittent failure to start...

FearlessLeadr · 03-06-2013, 11:11 PM

Quote:

Originally Posted by SouthArk370Z

Glad to hear it's working again. Keep the spare handy. It sounds like you fixed the problem (not just an intermittent that went away for a while), but the switch is likely to fail again soon.

According to the 2009 FSM, the interlock switch is a simple SPST switch - the module is looking for volts present or not. Some controls in the car are "smart", eg, window switches and SLU, but not the clutch interlock switch. Edit: Ie, the module doesn't know the switch is there until it closes.

Then shouldn't that mean that I could disconnect the switch entirely? When I press the button, it breaks the circuit, so shouldn't it just think the clutch is pressed if I disconnect the switch? I also tried a wire bridge and it didn't work.

mults · 03-07-2013, 06:34 AM

Quote:

Originally Posted by FearlessLeadr

Then shouldn't that mean that I could disconnect the switch entirely? When I press the button, it breaks the circuit, so shouldn't it just think the clutch is pressed if I disconnect the switch? I also tried a wire bridge and it didn't work.

I think that the ECU needs to "see" the switch open and close when necessary. If the switch is bridged like you say to keep it closed permanently, then the ECU does not see the change in state. I know when I try to start my car, the dash icon lights up that says to depress the clutch (switch closed) and then the car starts. If the ECU does not see the switch close, then the car will not start. It is a programmed sequence that has to happen otherwise, nada.

SouthArk370Z · 03-07-2013, 07:03 AM

Quote:

Originally Posted by FearlessLeadr

Then shouldn't that mean that I could disconnect the switch entirely? When I press the button, it breaks the circuit, so shouldn't it just think the clutch is pressed if I disconnect the switch? I also tried a wire bridge and it didn't work.

Since the bridge didn't work, it would seem that mults is right and the car has to see a transition. I suspected as much (it's not uncommon for interlock circuits), which is why I suggested using a switch.

FearlessLeadr · 03-07-2013, 01:35 PM

Quote:

Originally Posted by SouthArk370Z

Since the bridge didn't work, it would seem that mults is right and the car has to see a transition. I suspected as much (it's not uncommon for interlock circuits), which is why I suggested using a switch.

So, that means if I hold down my clutch, then start the car, then turn it off and try to start it again without releasing the clutch, shouldn't it not work?

SouthArk370Z · 03-07-2013, 02:15 PM

Quote:

Originally Posted by FearlessLeadr

So, that means if I hold down my clutch, then start the car, then turn it off and try to start it again without releasing the clutch, shouldn't it not work?

Try it and see. I'm just going by the wiring diagrams and a lot of things disappear into the ECM/BCM/&c where only Nissan knows what happens. It appears that the car is looking for a transition, but it may be less (or more) complicated than that.

FearlessLeadr · 03-07-2013, 09:44 PM

Strange, well, it hasn't done anything like it, so that must have been the issue. I'll just have to last until the new part shows up. Thanks for the help and interest.

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03-07-2013, 09:44 PM	#6 (permalink)
FearlessLeadr Base Member Join Date: Mar 2013 Location: Hawaii Posts: 10 Drives: 09 370z Rep Power: 14	Strange, well, it hasn't done anything like it, so that must have been the issue. I'll just have to last until the new part shows up. Thanks for the help and interest.