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I did some searching and found others with a similar problem, but no obvious solution. This just happened to me today. When I start the car the tach does its sweep thing, and then drops to zero. And it stays there, even though everything else works perfectly. The car runs and drives just like it should, but apparently I can cruise at 75mph at 0rpms.
Had the same exact issue with my 2000. Checked everything CPU, Can sensor etc. Finally replaced gage cluster. Problem solved. Marc at Vettnuts is where I got new Cluster and had correct milage flashed at Chevy dealer
That just seems extreme, to have to replace a whole cluster because the tach died. Weird. It's strange that the initialization works and the needle sweeps, but then nothing. I'm suspecting the signal is lost somewhere, will try to dig into it this weekend.
Thanks for the info. The weird thing is we went for a long drive today and the tach started working again. Then it stopped again. Then it started again. So I think I have some kind of connectivity issue. I pulled the codes and here's what I've got.
10-PCM P0654 H C - Engine Speed Output Circuit, looks like the tach
28-TCS C1247 H - can't find this one
58-SDM B0090 H - can't find this one
BO-RFA C2100 H C - yep one of my tire sensors is out
BO-RFA C2105 H - interesting, this one works fine
I had the same issue with the cluster not reading RPMs. On my car the cluster was fine, the wiring from the PCM to the cluster had an open. Had a new wire run from the PCM to the cluster to fix the issue.
If you want to look at the wiring here is the schematic.
Last edited by RedRiderZR1; Apr 15, 2018 at 12:19 AM.
I also have a tach issue. It wants to stick at lower rpms but once past 2000 rpms it works perfectly. Usually after a day or two of driving it will begin to work normally again. The HUD is showing the rpms accurately.
I had the same issue with the cluster not reading RPMs. On my car the cluster was fine, the wiring from the PCM to the cluster had an open. Had a new wire run from the PCM to the cluster to fix the issue.
If you want to look at the wiring here is the schematic.
Thanks! That is what I need to start troubleshooting. I really need to pick up the service manuals. FWIW it started working again for at least a little while, definitely something squirrelly in the connection.
Originally Posted by wayneinvirginia
I also have a tach issue. It wants to stick at lower rpms but once past 2000 rpms it works perfectly. Usually after a day or two of driving it will begin to work normally again. The HUD is showing the rpms accurately.
My HUD isn't working either, so I had nothing. I need to get the ambition to pull the dash pad and dig into the HUD.
I had the same issue with the cluster not reading RPMs. On my car the cluster was fine, the wiring from the PCM to the cluster had an open. Had a new wire run from the PCM to the cluster to fix the issue.
If you want to look at the wiring here is the schematic.
did you just run a wire from the pcm directly to the icp?
did you just run a wire from the pcm directly to the icp?
Yes that is what we did for RedRiderZR1's car.
However, check the connector for the IPC. I had a bad pin in the connector that was not making good contact on my car. Pulled it out of the connector and tweaked the pin so it made good contact which corrected the issue with an intermittent Tach.
Yes that is what we did for RedRiderZR1's car.
However, check the connector for the IPC. I had a bad pin in the connector that was not making good contact on my car. Pulled it out of the connector and tweaked the pin so it made good contact which corrected the issue with an intermittent Tach.
Gary
when you ran a new wire, did you run it in parallel to to original wire or did you replace the oe wire all together? I'm in the process currently and have cut and replaced the pcm wire and have run it into the interior via the wiring grommet and sealed off the original wire.
I'm getting ready to pull the ipc but don't want to have to do this twice.
Tach died
