P0654 Engine RPM Circuit Malfunction -DEF ?

[wantsum411]

I have just finished a '68 Firebird with a '04 GTO/Auto swap that seems to hit on about 4 cyl under a load but after clearing the codes it will run good for a lil bit but this code comes back.P0654 is the only code as of now Engine RPM Output Circuit Malfunction .I have searched all the stickies ect & cannot find a Definition or details .
Mtr has a MS3 cam & full exhaust .Thanks for any help .

[planethax]

post your file so I can see exact setup to look up

[wantsum411]

You want a scan log of start up & idling ?

[planethax]

looking for your tune, the Pcm file you are using is for an 04 GTO?
You using 04 GTO Engine harness and Cluster?

[Montecarlodrag]

The problem is a lack of tach hooked to the PCM output (white wire), it will detect an open circuit and set the DTC.
If you are not using it, disable that code to the tune and it will never bother you again.

[wantsum411]

Ok ,the customer provided a cutdown factory harness off the '04 GTO .The Tach lead is not hooked up to a tach & there is no other wires lose or left out of the harness.Also I have not done a Crank Variation Relearn as of now.I used the Krambo idle tune to get here as it starts good & we are trying to dial in now.
Here's a copy of what is in it now .

[planethax]

ok so as montecarlodrag said, set P0654 to 3 "No Error Reported"
This is caused from the Pcm seeing there is no tach hooked to C2 Term 10 of the Pcm

[wantsum411]

Easy enuf,Could this be my missing issue or the need for a Crank Variation relearn ? It is almost like a failsafe mode sound when you give it much gas or try to rev it up.On a short ride yesterday it was on all 8 cyl for a lil bit & back to the missing .
My shop specializes in conversions & have had alot that required no Relearn for the Crank .THANKS for all the help !http://bluecollarlsx.com/

[planethax]

Post a log of it going into rep mode
Logging Map and air flow

[wantsum411]

It will be this eve as other jobs are in process now .