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Old 06-08-2011, 08:22 PM   #1
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Default Testing ICM wires

I'm trying to diagnose a no start problem, testing the ICM/wires using a multimeter according to this guide:

http://easyautodiagnostics.com/gm_ig...n_module_2.php and also:
http://troubleshootmyvehicle.com/mai...p_sensor_3.php

I'm a newbie with a multimeter so just a simple question to confirm which is the right wire to probe:

M- RED with BLACK stripe wire.
CAM and CRANK Position Sensor Ground (-).

N- WHITE with BLACK stripe wire.
12 Volts to CAM and CRANK Position Sensors.

The troubleshootmyvehicle seems to have a typo mislabeling the N and M wires and warns of shorting them. So if I am probing the N wire(12volts according to this) I would use the RED test lead here and BLACK lead to negative on battery? And then to test M wire (ground) I would use the Black test lead and the RED to positive on battery? It makes sense but want to make sure.

Also since I'm a newbie and all I might as well confirm that where it says "12 volts TO cam/crank sensors" means that this is SENDING to the sensors, and that I have to have the ICM plugged in to do this test? (This is to test the ICM, so then to test the Sensors I would probe the wires FROM the Cam/crank sensors and wouldn't need the ICM to be plugged in here, right?)
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Old 06-08-2011, 08:29 PM   #2
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Yeah that other site there has the N and M wires reversed, the red wire is positive according to them which makes sense. Since I'm learning and all, is there a way to figure this out on my own using a test light (without shorting out anything!)

Thanks.
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Old 06-08-2011, 08:31 PM   #3
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Your DVOM will not short any wires out.
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Old 06-08-2011, 08:49 PM   #4
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Thanks for the reply, that'* encouraging!

Do you happen to know off hand which is the right wiring? Is the red wire M the ground like this says?

Also since your here and knowledgeable and all, I was wondering if K (engine ground) is normal to be missing the female end on the plug (the only end missing on my icm plug)

I probed the K wire anyways and was getting under 11volts, could this be enough to stop the ICM from working?

Thanks again Dan
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Old 06-08-2011, 09:04 PM   #5
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Your not going to get 12v all the time, the write up should say battery voltage. Check what you have at the battery and you should have about the same when check P to ground, and K to positive.
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Old 06-08-2011, 11:07 PM   #6
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It was about 1.5 volts less than the battery. Is that anything?

I checked the N and M voltage and was getting .06 readings. I double checked the P wire again and it now gave .06 (was about 10.5 first I checked)

Sorry this is probably all a newbie mistake somewhere, but I took your word that I wouldn't short anything with the multimeter and switched the leads. I then saw about 10.5v at the P wire. So then I test the M and N again (reversed) and I'm getting about 1.5 less volts than battery. So it seems the ICM is ok, but does the lesser voltage between the battery and the wires sound like a culprit?
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Old 06-08-2011, 11:09 PM   #7
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I have no clue why the leads were reversed other than when I probed N and M without knowing the right polarity, the multimeter autoadjusted?
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Old 06-08-2011, 11:13 PM   #8
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You should see 10 to 12 Volts on the multimeter.
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