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Discussion Starter #1
Wondering if anyone out there would know of what this problem is. 2000 7.3 psd. Every time I go into pending codes with any of my shops snap on scanners the idm relay 85 wire starts as a good ground but once I hit continue for pending it clicks and now becomes a hot wire and no longer have power running thru 87 on relay but have power at 30 still. What is idm enable out on pcm as that is where 85 wire comes from to relay
 

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The PCM provides a ground for 85 on the IDM relay. When it opens the circuit, the relay will drop out. Pin 30 is always powered and 87 is only hot when the relay is pulled in (from the ground thru the PCM circuit). So what you're doing with the scanner is switch off the ground to pin 85. 85 will show hot (with key on) because there's no ground path. It may not be a problem, just the way the scan tool works.
 

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not sure I understand. 85 starts as a ground but then goes hot after start up and drops 87 power to idm. So the 85 wire goes to pin 80 on pcm which is idm enable out on schematic so does pcm start it as a ground then changes it to power to cut power to 87 which is power in to idm. Also when the relay cuts out I cannot start truck until I key of and back on to reset relay. I have tried even a bluepoint palm reader and centech all cut power to idm
 

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The PCM is a switch that controls the relay coil. On key-on the switch closes and grounds the relay coil circuit. You'll read ground on the PCM side of the relay coil, because it's grounded. When the switch in the PCM opens, you'll read battery voltage, because there's no current flowing (and no resistance across the coil).
 

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Discussion Starter #5
The PCM is a switch that controls the relay coil. On key-on the switch closes and grounds the relay coil circuit. You'll read ground on the PCM side of the relay coil, because it's grounded. When the switch in the PCM opens, you'll read battery voltage, because there's no current flowing (and no resistance across the coil).
So why would any scanner I have used keep truck from starting unless I key off and back on to ground coil again.
 

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I have had issues where attempting to read data from a scantool will cause a powerstroke to shut down. I don't know why, but it happened with my old Snap On brick, and with my old OTC Genisys. It has never happened with Autoenginuity, though.
 

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It has never happened with Autoenginuity, though.
I have had AE kill my engine a couple times.
ataylor66, your issue may just be caused by the scan tool.
 
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