Chrysler Repair: tach intermitant: Ram 2500, crank sensor, diagnostic capability

Question
I have a 99 ram 2500 with the cummins 24 valve turbo and lately the tach is intermitantly cutting out. where could the tach pickup be?

Answer
Hi Steve,
There is no separate tach pick-up, rather the crank sensor that is needed for the ignition system shares its pulse rate with the tachometer on the digital data bus. The fact that the tach only is dropping out usually means that the issue is with the tach gauge itself, not the signal data to the cluster because the other gauges get their data the same way. This is all based upon how the car lines were designed in the latter 90's. So you might want to see if there is a self-diagnostic capability on the cluster proper. On the vans you hold the trip and reset buttons in, or if there is just a reset then hold it in, then turn the ignition to run and hold the buttons in until the word "code" appears in the odometer window. Then release the buttons and watch for any code numbes to appear in the window. Any number other than 999 is relevant; 999 means no problems detected. I don't know that the Ram has this feature, but give it a try. Otherwise check for whether there might be a plug-in module on the edge of the tachometer gauge which might be replaceable called the tachometer module which was the earlier 90's car design.