Dash Tach possessed....
07-21-2010, 12:36 PM
#1
TECH Enthusiast
Thread Starter
iTrader: (4)
Join Date: Dec 2005
Location: Nashville, TN
Posts: 612
Likes: 0
Received 0 Likes
on
0 Posts
Dash Tach possessed.... Installed a shift light and micro edge nitrous controller using the tach output at the PCM and just noticed the Tach will bounce around, drop to zero then jump up sometimes not work at all and other times itll sit right where its supose to. HPtuners tach shows the RPM right on the money with no bouncing around. Anyone seen this before?
07-22-2010, 09:40 AM
#3
TECH Addict
iTrader: (14)
Join Date: Feb 2007
Location: Owasso, OK
Posts: 2,342
Likes: 0
Received 0 Likes
on
0 Posts
Make sure the wire that goes to the tach is still making good connection. You didn't say how you spliced into the wire so just make sure you didn't cut it or something.
Thats all I got.
Thats all I got.
07-22-2010, 10:10 AM
#4
TECH Enthusiast
Thread Starter
iTrader: (4)
Join Date: Dec 2005
Location: Nashville, TN
Posts: 612
Likes: 0
Received 0 Likes
on
0 Posts
It doesnt seem to matter if the nitrous is on or off soI dont think its a voltage drop. The line that is run back to the shift light and microedge is tapped about 8" from the PCM. the shift light works prefectly at any RPMso the signal is good. Im picking up the switched 12 V that feeds the two from the cig lighter... grounds run back to a central lug under the center console.
Where is everyone else tapping in to get there tach signal?
Where is everyone else tapping in to get there tach signal?
07-25-2010, 08:39 PM
#5
Sorry I am new to the LS6, but are you using the tach output to the actual gauge for your tach reading?
Just having extra taps of a PCM can cause the stock equipment to go nuts. I had issues with the VSS on my cobalt. It would work fine on the GPS but it would cut out to the PCM at times. The computers are sensitive and they don't like even the smallest electrical changes some times.
I have had good luck tapping one of the ignition coil control leads. Depending on the gear you are running it might not have the right multiplier to get the RPM right however. But there is less chance to mess up a reading on IPC.
Just having extra taps of a PCM can cause the stock equipment to go nuts. I had issues with the VSS on my cobalt. It would work fine on the GPS but it would cut out to the PCM at times. The computers are sensitive and they don't like even the smallest electrical changes some times.
I have had good luck tapping one of the ignition coil control leads. Depending on the gear you are running it might not have the right multiplier to get the RPM right however. But there is less chance to mess up a reading on IPC.
07-26-2010, 07:32 AM
#6
TECH Enthusiast
Thread Starter
iTrader: (4)
Join Date: Dec 2005
Location: Nashville, TN
Posts: 612
Likes: 0
Received 0 Likes
on
0 Posts
Forgot to update this! it was actually due to the battery going dead and needed a "crank relearn" ? Im not sure what that means but it was my buddies car and when he went to the dealer thats what they said it needed... either way its fixed 
