Grounding 32/34 C1 advice

[McKenna]

Okay guys I've been lurking on here for 4 or more years slowly picking away at my LQ4 swap.

Trucks a 1970

Trans is a 2000 nv3500 (5speed manual) mated to an 04 DBW LQ4.


After first start up It runs great however I have an issue where my engine will not rev over 1400 rpm.

Sent my ecu back to insure that "abuse mode" (there are two) was turned off to allow the truck to rev.

Still nothing.

So after some more reading I grounded pins 32/34 on connector C1(blue) which is supposed to initially make the computer think it's in Park/neutral.

Low and behold it'll rev up it appears to run great.

Will I run into any trouble by leaving 32/34 permanently grounded? I can't find any information throughout my searches.

VSS is also hooked up and working

[BR3W CITY]

Do you have an NSS in the vehicle to hookup to? Either on your shifter, or from the range sensor on the trans?

[JMac11]

Watching this one....

[McKenna]

I would presume the neutral safety or clutch safety was built in on the clutch pedal on the 2000 Silverado.

My 1970 never had an operational NSS in the years I had it, I'd be shocked to find out it was ever equipped with one.

It was a factory 250/sm465 truck.

I could care less if I had a NSS as it hasn't had one in the 20 years it's been in my family.

My friend who unlocked my pcm said he used the stock LQ4 mapping and put the nv3500 Trans segment in there.

The truck does start fine, but without pin 32/34 grounded it wouldn't rev over 1400/1500 rpm.

When in gear on stands it still wouldn't rev past 1400 even tho the VSS was registering 20k/ph

Once grounding the wires all seems fine it'll rev and drive on the stands (I have yet to actually drive the truck)

I understand that the gear selector or N/P function is good to have on an automatic as it adjusts idle for drive position, but for my manual truck I will be in neutral or have the clutch in at any stop light or while parked.

In theory any time the trucks in gear and the clutch is released I will be on the go pedal unless I'm coasting/engine braking in which rpm should already be up past the idle point. So I don't see how the P/N will effect my performance, however I could be wrong.

I don't mind leaving the 2 wires permanently grounded I am more so asking if this is something that could cause me issues down the road.


I could try putting a switched ground on it to see if it'll rev after seeing switched ground, then try installing a NSS but I don't see a need for it as it was never there to begin with

Thanks for reading and thanks for any input you guys have.

[BR3W CITY]

Are you throwing any codes as a result? Is it actually triggering the Limp?

Technically you shouldn't need the NSS, hell I haven't run one on an auto in a while, but I also have my idle settings setup to accomodate the loading without the NSS input.

The NSS itself won't hard-limit your RPM, but its possible that it might be triggering an error that IS stopping you. For example, if a crank or cam sensor was replaced, you can't trigger the relearn procedure. So there are NSS-related problems, but again, in the ECM some of it can be cleaned up pretty easily.

You can also just put a momentary on it, or just put a relay on it to trigger a momentary ground on the circuit.