Thealien

iTrader: (2)

I am using the factory (1972 GMC Jimmy) Dash bezel and gauges. I have everything working (I believe, don't have a scanner yet) except the tach. I hooked the tach wire from my 1972 tach harness to the wire marked tach and I ran a power wire to the tach just like it was and working before the swap. The engine starts and runs fine, no MIL/CEL while running but the factory 1972 tach is not moving. The engine is a 2005 5.3 and the PCM has blue/green connectors.

What can we do to get my tach working.

What PCM pin should be my tach signal?

Thanks
Mark

I don't know the settings in the PCM as I did not do the tuning. I have a PM to the tuner and I will post what he has to say but thought I would ask the knowledgeable members also.

Pocket

iTrader: (22)

Some tachs need the booster wire

Thealien

iTrader: (2)

Is the booster wire the 680 ohm 1/4 watt resistor or?

fptransport

when I did mine,, I am using a autometer tach,,, I had to use the resistor to the "tach" line from the pcm to the tach, just use the resistor you mentioned, and plug one side to the tach wire and the other side of the resistor to a 12v ing. mine has worked, but when at idle my needle moves up and down just as if I had a big lobe cam in the engine., but it only does it at idle...

928vette

I believe that the tach signal produced by the PCM is a digital signal and can't be fed directly to an analog tachometer.

Here is one product that I found (haven't used it):
http://www.nookandtranny.com/mm5/mer...ry_Code=GAUGES

For myself, I just purchased two aeroforce OBDII gauges:
http://www.aeroforcetech.com/
I haven't installed them yet, but if they work as advertised, they will display RPM, water temp, and anything else that the OBDII knows about and you can set 'alarm' values.

Pocket

iTrader: (22)

Nonsense, 4th gens use analog tachs along with pretty much all older cars. The signal itself is just weak and needs to be amplified for some tachs to read it

gofastwclass

iTrader: (2)

Your first statement was incorrect.

The tach signal can be sent to a standard tach direct from the PCM but the tach has to be set for 4 cylinder (yes weird I know). The Dakota Digital box is for people who can't or won't change the tach (or with factory or vintage instruments like Alien and I) and don't have access to change the output in their tune. Originally I installed one on my car but the tach output was fine, just incorrect. Now that I have tune software I could change the output in the tune but the box is already wired in and hidden so...

If I remember The Alien's build he is like me and trying to keep the factory feel about the interior so that solution won't work - but it looks cool in a high tech way.

Alien, you may have to do the resistor trick to get the tach working since your PCM is newer than 2003.

Thealien

iTrader: (2)

Thanks, I'll let you know if the resistor works when I get the chance to try it out!

Mark

fptransport

as mention b4 the resistor trick will work, just set the tach 4cyl,, thats what i did on mine,, but mine is kindof jumping at idle

lamdenali

iTrader: (5)

Will 680 ohm at 1/2 watts will do cuz radio shack dont have 1/4 ?

busta9876

iTrader: (3)

yup that will work fine as well....1/2 watt

lamdenali

iTrader: (5)

Thx Guy I just install the resitor and now my Tach working now.

Thealien

iTrader: (2)

I installed the resistor and my Tach now works but reads low. I guess I have to buy HP tuners or get someone to let me use theirs and buy a couple of credits to adjust the output in the PCM?

gofastwclass

iTrader: (2)

Too bad you're not near me.

Option 2 is using the Dakota Digital converter box. It will allow you to change the 4 cyl factory output to V8 (or anything you need it to be) to match your factory style tach.

Thealien

iTrader: (2)

A local tuner changed something in the PCM and the tach reads fine now!

bronx_peanut

I tried to use the resistor on my swap and it did nothing. My tach is not working any ideas? I am using a stock tach in my Trans am.

BillyBurb

i have a 69 suburban that I swapped an 2002 5.3 4L60E motor in my suburban came with the factory tach I'd like to keep it I saw a guy at the Pomona swap meet in December an he got his factory gauges tach speedo to work he used the black box for speedo but I don't remember what he used for tach please help I want to keep my dash original. Thanks

Project GatTagO

iTrader: (7)

The answers are in this thread.

Andrew

Liltroy