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4.0 swap/VSS wiring

8K views 5 replies 3 participants last post by  Jak_Flash 
#1 ·
I put a 94 4.0 from a YJ in my 78 CJ7 with the AX15 and a Dana 300. I bought a 91 YJ Speed sensor and it has a two wire hook up.The wiring for the Speed sensor from the 94 4.0 has three wires. I bought the 3 to 2 wire conversion plug from Hesco..Which two out of the three do I hook up?
 
#2 ·
I have copied this from cjoffroad, never tired it but guys say it works. The Early 2 wire VSS is a simple mechanical switch, it makes and breaks a set of contacts internally using magnets and a reed switch. One wire is from the PCM which has a 5 volt reference internally, the other is the sensor return. When the 5 volts drops to ground, the PCM senses a trigger.

The later 3 wire VSS uses a Hall effects switch to make and break the connection between the sensor return wire and the ground wire. The 3rd wire is a 5-8 volt power supply to operate the hall effect sensor.

The 3 wire sensor colors are usually:
Wt/Bk = 5-8v supply
Wt/Or = Sensor return (signal to PCM)
Bk/LB = Common sensor Ground

With the 2 wire sensors, just connect the 2 wires to the Bk/LB and Wt/Or wires from the harness, you can disregard the Wt/Bk = 5-8v supply wire, it's not needed! It doesn't even matter which wire you connect to which pin on the 2 wire VSS, (but if the colors match, connect them!)

Hope this helps!
 
#4 ·
If I remerber right may have been from Marty So Cal, but not real sure. He hangs out over on priate and is real good with mpfi. The way I understand it is "you can disregard the Wt/Bk = 5-8v supply wire, it's not needed!"
Take a volt meter and see witch one has 5-8v and dont use it.
 
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