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2001 Mack CH sensor voltages


IHfarmboy

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my guess is you have a V-Mac III truck..  I have seen you post here before..  My suggestion is to buy,  (V-MacIII Book # 8-211) ...   it is a wealth of info..  jojo

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6 minutes ago, Joey Mack said:

Onyx, I'm glad you were able to post that.. I have a hard time posting pics lately,, jojo

Go into to your account and then my attachments. What’s your quota at? Mines getting up there so I may not be able to post pics much longer either. 

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Those speed sensors are variable reluctance. They induce their own A/C voltages. There is no specific voltage to test that is being generated by the sensor. The 5V signal that you see in the schematic is a sensing voltage to inform the ECU if the circuit is good or not. The only way to see if the signal is good or not is to hook up an oscilloscope and watch the A/C signal that is being generated. 

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17 minutes ago, Vmac3 said:

Those speed sensors are variable reluctance. They induce their own A/C voltages. There is no specific voltage to test that is being generated by the sensor. The 5V signal that you see in the schematic is a sensing voltage to inform the ECU if the circuit is good or not. The only way to see if the signal is good or not is to hook up an oscilloscope and watch the A/C signal that is being generated. 

Variable reluctance sensor….that’s it! I couldnt think of it so Hall effect was the closest thing that came to mind.

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14 hours ago, Vmac3 said:

Those speed sensors are variable reluctance. They induce their own A/C voltages. There is no specific voltage to test that is being generated by the sensor. The 5V signal that you see in the schematic is a sensing voltage to inform the ECU if the circuit is good or not. The only way to see if the signal is good or not is to hook up an oscilloscope and watch the A/C signal that is being generated. 

Why would I be getting 12v from the ECU and not 5v?  Could the ECU be bad?

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