Tachometer problem..help?
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Pro
Joined: Aug 2001
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From: West Palm Beach FL
Tachometer problem..help?
My tachometer has been sporatically working. It would go out when driving and I would tap the cluster and it would come back on. Recently the tach completely stopped working.
All the other gauges on the cluster have been fine...they still work and never turned on and off.
I am tied into the Tach wire ...it is running to another accessory (boost gauge) and it too is not showing RPM.
Where is the RPM signal generated...Crank sensor? and then where does it go....
What module controls the signal to the dash cluster..
Please shed some light on my problem
Tom
All the other gauges on the cluster have been fine...they still work and never turned on and off.
I am tied into the Tach wire ...it is running to another accessory (boost gauge) and it too is not showing RPM.
Where is the RPM signal generated...Crank sensor? and then where does it go....
What module controls the signal to the dash cluster..
Please shed some light on my problem
Tom
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Joined: Oct 2002
Posts: 16,477
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From: Gone
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St. Jude Donor '03
The white tach wire comes straight out of the PCM.
The first thing I'd do in your case, is get that car on a scanner, and see if the scan tool displays accurate rpm. If it does, it means your PCM is good, and the problem lies somewhere between the PCM and your tach and gauge.
Because you tapped into this wire, and the problem started intermittently, I would check the connection wherever you tapped into it. Might simply be a bad crimp or splice connection that left both your tach and gauge dead.
The first thing I'd do in your case, is get that car on a scanner, and see if the scan tool displays accurate rpm. If it does, it means your PCM is good, and the problem lies somewhere between the PCM and your tach and gauge.
Because you tapped into this wire, and the problem started intermittently, I would check the connection wherever you tapped into it. Might simply be a bad crimp or splice connection that left both your tach and gauge dead.
Thread Starter
Pro
Joined: Aug 2001
Posts: 724
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From: West Palm Beach FL
the problem didnt start right after the tapping of the wire....but I will hook up HP Tuners and see if there is a signal.....if there is I will check my tap/connection next..
If there is no signal...then does this mean the PCM is shot? With no other malfunctions? Or could it be a sensor? Not sure where the PCM gets signal from crank or cam sensors?
anyone know? the GM manual doesnt say where the signal originates from...
Thanks..
Tom
If there is no signal...then does this mean the PCM is shot? With no other malfunctions? Or could it be a sensor? Not sure where the PCM gets signal from crank or cam sensors?
anyone know? the GM manual doesnt say where the signal originates from...
Thanks..
Tom
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Joined: Oct 2002
Posts: 16,477
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From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
If you have HPT, definitely hook it up, scan and report back.
If it shows zero rpm with the car running, then yes the problem goes more complex...but before crossing that bridge, look at the obvious..There's too many rpm-based tables in the PCM logic for the car to run well (if at all) if the PCM has no ability to recognize engine rpm.
That simple fact instantly leads one to believe any indication problem must be downstream of the PCM.
If it shows zero rpm with the car running, then yes the problem goes more complex...but before crossing that bridge, look at the obvious..There's too many rpm-based tables in the PCM logic for the car to run well (if at all) if the PCM has no ability to recognize engine rpm.
That simple fact instantly leads one to believe any indication problem must be downstream of the PCM.
Advanced
Joined: Jan 2006
Posts: 67
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From: Austin Texas
I put some white faced gauges in my car and afterward had the same issue. My problem was with the plug at the back of the gauge cluster. I could wiggle it around and watch the tach go from working to being dead. I put some dielectric grease on the plug and it's worked fine now for a couple of years. Now I don't know if that had anything to do with it, it may have just gotten into a position that it likes and it's just a coincidence
. Anyway, hope this helps.
. Anyway, hope this helps.
