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Old 09-01-2011, 10:24 PM   #1
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Default LQ4 Crank Sensor

I have a question about crank position sensors on an 03 LQ4.

I am using the engine in a race car running in the "classic category" so that means no FI so I am running an MSD 6ls ignition box with a carburetor. Everything worked fine for the firsst season.

The last time i fired it up the ignition box smoked. The box is back at MSD for repairs but in the mean time i want to make sure everything else is ok.

My Question :

How do you test the crank sensor and cam sensor?

There are three wires going to each. One is power and one is signal. I guess the other is ground. when I put power on the system I have 12 volts at the power wire but also 12 volts on the signal wire. is this normal?

Thanks

Fred
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Old 09-01-2011, 11:52 PM   #2
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This test is for testing the ICM, but there are also tests for the crank and cam sensors. This should help you out.

https://www.gmforum.com/trouble-shooting-test-procedures-141/icm-test-299761/
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Old 09-02-2011, 09:50 AM   #3
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So... it seems I should only see 5 or 6 volts when the sensor is being triggered.

Thanks Dan
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Old 09-03-2011, 08:24 PM   #4
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bought a new sensor today. hooked it up to the harness and put power on the system. (sensor not installed in block). Found that if it trick the sensor by holding it near anything steel voltage reads 12. move the sensor away from steel and voltage reads 2.5. Stuck old sensor on plug and same results... hmmm. seems old sensor is ok.

I am curious to hear what MSD finds cause there is not a whole lot else that could be wrong. MSD has an easy hook up... power , ground and tach. all other wires are pre-fab in a harness with factory plugs. harness was working ok last year.

Fred
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