Clutch switch....or lack of one

[cobra30689]

I have a 4.8 with a NV3500 in a Jeep YJ, manual transmission calibration. I read somewhere that the PCM will only transition to the main spark tables when the clutch is released. My issue is this....older YJ's don't have a clutch switch, or even any provisions to attach one (newer TJ's do however). Tech2 shows the clutch being engaged all the time, as like the TCC circuit, the PCM is looking for 12v when the clutch pedal is released. Am I correct in my assumption I am running solely on the idle in drive spark table? My only recourse may be to wire the clutch switch wire to switched 12v to allow the PCM to use the main spark tables, but how would that affect return to idle and idle timing? I haven't touched the spark tables in the tune because the engine is stock, but I attached it anyway. Thoughts?

[gtstorey]

Is it truly looking for a switch on that or does it need a position sensor. If just a switch you should be able to add a switch somewhere someway. But you need to confirm what it’s actually looking for. I think that a lot of these are looking for a ground or a break in the signal instead of 12v.

If looking for a position sensor, it will be much harder.

[cobra30689]

It's a 2002, so it's only a single pole switch, PCM is looking for a break in the circuit. P0704 is of course disabled in the tune at the moment.

Screenshot 2024-03-23 102620.png

[gtstorey]

I would have said from the symbols on the diagram that it is a variable resistance switch, but GM changes the symbols so much that it would have to be confirmed in the manual. It does say “position”.

[blindsquirrel]

'Up' and 'down' are positions, technically. The diagram is an on/off switch. Plus, the switch vs. sensor thing.

[cobra30689]

'Up' and 'down' are positions, technically. The diagram is an on/off switch. Plus, the switch vs. sensor thing.

The second part of my question remains unanswered however......am I running solely on the idle in drive spark table with the PCM registering the clutch being engaged all the time?

[blindsquirrel]

Dunno, wire up a temp momentary switch and see.

[grubinski]

The second part of my question remains unanswered however......am I running solely on the idle in drive spark table with the PCM registering the clutch being engaged all the time?

Set your whole idle table to X degrees and your main table to Y degrees. Then log and see what you?re running at cruise.

[Alvin]

I have a 4.8 with a NV3500 in a Jeep YJ, manual transmission calibration. I read somewhere that the PCM will only transition to the main spark tables when the clutch is released. My issue is this....older YJ's don't have a clutch switch, or even any provisions to attach one (newer TJ's do however). Tech2 shows the clutch being engaged all the time, as like the TCC circuit, the PCM is looking for 12v when the clutch pedal is released. Am I correct in my assumption I am running solely on the idle in drive spark table? My only recourse may be to wire the clutch switch wire to switched 12v to allow the PCM to use the main spark tables, but how would that affect return to idle and idle timing? I haven't touched the spark tables in the tune because the engine is stock, but I attached it anyway. Thoughts?

That isn't true. If throttle is opened its going to use the main spark tables. Clutch doesn't have anything to do with what spark table it's using.

[cobra30689]

That isn't true. If throttle is opened its going to use the main spark tables. Clutch doesn't have anything to do with what spark table it's using.

Excellent! The answer I was looking for. Thank you.