IS this redundant in a manual tranny? If not when is it used?

When dipping the clutch? What does the

Clutch switch on/off effect in terms of other functions. Gear detection?

 

AFAIK it's only there to allow starting only with the clutch depressed. I honestly didn't even realize until just now that it goes to the ecu on obd2 vehicles.

The computer doesn't need clutch input to figure out what gear it is in, only vss vs. rpm (and of course a table of gear ratios to reference)

 

Never had any manual 4 cylinder cars use any of the C connector pins past C20. There isn't any clutch switch input required to the ECU. The clutch switch is a neutral safety switch for the ignition.

AFAIK all of the C connector inputs past C20 are for automatic and ATTS trans sensors. To be more specific, C29 is the ATPNP or Automatic transmission gear position input. Not required with a manual trans, and an AT ECU will throw codes unless modified to bypass the AT circuits.

 

It's definitely listed in the pinouts, I looked. 92-95 was only on the VX, maybe this carried over to the HX?

 

Listed as what? The ATPNP or clutch input? I've seen it listed for AT inputs not a clutch switch... This being said I have mainly worked on OBD1/2 Accords and Preludes and OBD1 Civics.

The OBD2a Accord and Prelude Shop manuals have Pin C29 listed as the automatic gear position input (ATPNP).

Besides, the OP hasn't even listed what chassis or ECU he is working with.... That info would definitely help clarify some things!

 

I believe all OBD2 vehicles are required to have Engine Assisted Braking Technology; if the ECU does have a circuit for clutch input, it's probably strictly for that.
Gear detection is by RPM and VSS, not clutch related.
What's the point of this anyway?

 

Thanks for the inputs. (Clutch SW is not used for gear detection; Pins past C20 are for auto trans. - Seems like CLSW is not used on a OBD2a manual.

BTW, my was greasing my clutch pedal assembly, and i could see a OEM sensor wired to the clutch pedal........ Mystery

Need to used pin C20 for a digital (window) input.....

 

Yes, the "OEM sensor" attached to the clutch pedal is the clutch interlock switch. It's basically the same thing as a neutral safety switch in an automatic. Car won't start unless this is actuated.