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Tach drops to zero

A

ahill261

New member
My 3.8L SC, 2001 Grand Prix has started to develop a problem. The tachometer sporadically drops to "0" and the TCS comes "on." On occasion, the "check engine" light comes on also. When this happens, there is a slight sputter but the comes continues to run. Upon shutting the engine off and restarting it, the tach and TCS returns to normal. Will this eventually stop my engine and what is wrong with it?
 


Have you pulled the code?

It sounds like a crank sensor. However having the code would help out. The TCS is odd, usually you don't get that with the crank sensor.
 
Mine had the same thing happen. Didn't really look into rectifying the issue but the gist that I'm getting is that it's the CPS, as people have mentioned. Good luck!
 
My '99 is doing the same... I will check into the cps and let everyone know how it goes.


Thanks.
 


If there is an interruption in the signal from the crank position sensor to the tach due to the CPS going bad, the tach will drop to 0 and not move again till you reset it by shutting the car off and turning it back on. It will also often trigger the "TCS Off" light if 1 of the 2 needed signals coming from the CPS is interrupted, so given your symptoms, it's almost a guarantee that it's the CPS.
 
My 2000 GT 3.8 had the same problem. It would then stall for no reason while driving on the highway, in the city, stopped at a light. Taking the advice from here I replaced the crank sensor haven't had a problem since.
 
If... And a big IF the crank sensor doesn't fix the problem, the wiring harness near the PCM that passes the evap/condenser gets uncomfortably close and over time can rot out wires from HEAT in that portion of the harness (experience).

If all else fails, you can check there (but only as a last resort).

:)
 
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