i dont have any DIS or IDM codes. i do have another DIS laying around, is there any harm in swapping DIS' back and forth to trouble shoot it?J.D. said:I'm not certain about this, but here goes. The tach is driven by the IDM signal from the DIS. If you have any IDM error codes (18, 212, 218, 222, 224, 226, or 241) then that will point to a problem with the DIS.