I have a 06 Ram 1500 SLT 4.7l and the tachometer has started reading low while at a stop light or just sitting in the driveway. It actually is idling fine and sometimes will not be affected but other times the idle on the tach is reading 0 or 100 rpm. I pulled the Throttle Position Sensor and replaced it but the idle was way to high and it would burp when applying throttle. I then switched back to the original TPS and reset the check engine light that then appeared. I pulled the connection to the Crankshaft Position sensor and cleaned it but did not replace it since I do not have one onhand. Any ideas as to what it may be? I did the trick with holding the Trip reset while turning the key to on and the gauges went through its cycle. Any help on what it could be making the tach show way to low and be jumpy?

 

If the rpms are not actually low, you probably just have a bad tach. It gets it signal from the PCM. (computer)

 

I have been having the same problem with my 2002. I had just changed my TPS because of a check engine light. I looked at everything and then decided to tap on gauge cluster and needle went back to normal. Still has problem, assuming gauge is bad. I did replace cluster under warranty years ago. Does whole cluster have to be replaced to fix this ya think.

 

mine goes backwards.. starts at -0 and goes around the otherway.. stupid tach

 

Lmao!!!!