RPM’s not registering on SMX-What to check for

[IslandStyle]

Hello All, I have a 5.9 12V 6BTA5.9 and have added the SMX digital gauge. The SMX would show RPMs when it was over 1k and anything under it didn’t really show a good reading. I just replaced the Cummins Magnetic Pickup Speed RPM Sensor and adjusted it the way I was instructed too. But now I have no RPM’s at all showing up. Any idea where I should start to trouble shoot this problem? thanks in advance for the info!!

Topic

[Corey Schmidt]

The mag pickup is a DUAL output device… both pairs output a square wave RPM signal… one is meant for the on-engine pre-heater, the other for the TACH.

Make sure the pickup is installed correctly:

How To Install a Magnetic Pickup to Drive a Tachometer

[IslandStyle]

I am using the mag pic up that has 4 wires coming off of it. The original 2 plug, one plug is white and green and the other plug is black and red. Can you tell me what wires go to what? thank you in advance.

[Corey Schmidt]

To me it sounds like a wiring issue…. check the GREY wire direct from the mag pickup up to the dash…. there could be a bad connection somewhere. Also, make sure that the other wire that goes to BAT NEG is also in good shape…. no ground = no RPM signal.

[Author]

Replies