slick00m

iTrader: (8)

I have an 89 IROC originally LO3 305 TBI. I have swapped in an 03 6.0 LQ9. I have my stock tach connected to PCM C2 (green) pin 10 (white); it’s labeled as Engine Speed Signal. But I’m not getting anything on my tach. It will jump when I turn the key on but nothing after that. The tach was working before so I don’t think that it's bad. I have done a lot of research and searching and this is how I understood that it needed to be connected. Am I missing something?
Thanks,
Ryan

the_merv

iTrader: (88)

What Harness are you using..

Speartech

iTrader: (14)

The 03 and up truck PCM's have a different tach signal output and a lot of factory tachs won't work directly from it. If you add a 5000 ohm pull up resistor between a 12 volt ignition line and the tach signal wire, you tach should come right to life.

slick00m

iTrader: (8)

Great, thanks John. That's what I was hoping, but I was scared to try it without some input.

the_merv, It's the factory harness.

Thanks for the quick help.
Ryan

exodus

iTrader: (15)

HOLY CRAP, this guy's good!

the_merv

iTrader: (88)

Look what he does..

exodus

iTrader: (15)

yes i know, that is why HE did my harness and pcm for the formula

LSRacing

iTrader: (5)

Is the same true on a 02 corvette PCM? Its drive by wire and im having the same problem. Thanks

Speartech

iTrader: (14)

Yes it's the same. You can either add the resistor or you can also activate it in the tune.

tracar91

iTrader: (1)

John, what do you activate in the tune? I've got the same issue ('01 pcm and harness/ 91 Z28 guage) and I'm heading to the local dyno tune shop on Sunday. This is one of the issues I wanted to address.

Thanks

Speartech

iTrader: (14)

You can enable tach pull-up in LS1 Edit in the engine test parameters section. If that's not in your software editor, you would need to go the resistor route.