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PCM testing

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Old 09-19-2017, 12:48 PM
sinapu sinapu is offline
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PCM testing



So, I decided to jump in today with both feet.. after checking out the VGT connection, through the doghouse I accessed the PCM and the middle connector, pins 10 and 11 . I used a test light with a good ground and a mirror to test for power at each pin, unfortunately there's no voltage from each one. It runs fine, just has no turbo boost. Can anyone verify that I should be seeing voltage with the key on engine off senerio?
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Old 09-19-2017, 01:35 PM
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Not sure why you'd even mess with that. Have you code scanned the truck? Have you checked for boost leaks at all the CAC and y-pipe joints?
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Old 09-19-2017, 01:53 PM
sinapu sinapu is offline
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Yes, I've been retesting this issue for months and had no voltage at the VGT plug, so I went back to the PCM where the voltage comes from.

I've been getting the P2262 code for months, and it has very little low end power.

Thanks for your reply
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Old 09-19-2017, 04:16 PM
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P2262: MAP hose, MAP sensor, CAC system leaks, Intake leaks, EP
sensor, exhaust restriction.

Have you checked the MAP sensor hose nipple in the intake for an obstruction? That's the first place to start. If the map sensor can't read boost pressure you won't get the PCM to command any. Also, replace the MAP sensor with a known good one (borrow one from any 6.0 or 7.3) and see if that helps. Also, have you checked the EP sensor tube for a restriction or plugging? Same as with the MAP sensor. Do you have something to read boost pressure with besides the dash gauge?
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Old 09-19-2017, 04:31 PM
sinapu sinapu is offline
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Quote:
If the map sensor can't read boost pressure you won't get the PCM to command any.
Thank you so much for sharing that simple sentence, it's taken me almost a year to understand that fact. Not that I'm anything more than a forum/ YouTube mechanic. That makes total sense now.
I have checked the long tube on the left side of the doghouse, many months ago. Took me hours to screw the damn thing back in.. I do have the Forscan app on my phone which seems to have great reviews so far. . That's how I've been reading the codes and setting up different gauges. Think of mounting an i-pad on the dash and have it there permanently. I'll let you know what I find.

Thanks again
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Old 09-19-2017, 08:56 PM
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One thing you don't want to do is shove the meter probe tip into the connector.
You always go from the back side of the plug or you run the risk of stretching the
pin sockets. The technique is called Back Probing.
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Old 09-21-2017, 05:42 AM
sinapu sinapu is offline
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Quote:
Originally Posted by Yahiko View Post
One thing you don't want to do is shove the meter probe tip into the connector.
You always go from the back side of the plug or you run the risk of stretching the
pin sockets. The technique is called Back Probing.
After you told me about this last week, it's the only way I test wires now. Thanks!
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Old 09-21-2017, 05:47 AM
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So yesterday, everything checked out with the MAP sensor but I was looking around at a few things while I had it apart. Does anyone know what this plug goes to?
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Old 09-21-2017, 05:50 AM
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Quote:
Originally Posted by sinapu View Post
So yesterday, everything checked out with the MAP sensor but I was looking around at a few things while I had it apart. Does anyone know what this plug goes to?
Glowplugs. Green one plugs into GPM
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Old 09-21-2017, 07:23 AM
sinapu sinapu is offline
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That's actually pretty good because I don't have any problem with the glow plugs.
I have voltage to the MAP and the tube is clear and looks normal. I looked back at the sensor PSI historically and see that it hasn't been much higher than the 14.6 it is normally at sea level. I'm going to put it all back together and take some new readings today. Thanks for your input
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Old 09-21-2017, 07:30 PM
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I put it all back together today and took a drive, not much has changed yet but I took some new screenshots going down the highway at 70 , just for reference. I do have a lot more to choose from but chose ones I thought to be applicable. Maybe this will tell me where I need to go next..
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Old 09-23-2017, 04:46 AM
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If that is running down the highway I would say you might have maf issue (not sure if it matters or that I am correct) and possibly a stuck turbo. I assume you have checked that there is continuity between the vgt connector and the PCM connector?

I am just guessing here.... I am sure someone else will chime in.

Richard
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Old 09-23-2017, 09:37 AM
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Good morning,

I made a bit of headway by changing out the MAP sensor this morning and took it for a ride. Has a lot more power!
I've read in a few different places that the baro pressure and Map pressure need to be within a couple of lbs of each other, which is not the case.
Also still getting a couple of codes, but not the dreaded p2262 anymore, thanks!
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Old 09-23-2017, 09:57 AM
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MAP,BARO and EBP should all read with in .5 psi of each other. What year make and model of vehicle do you have? It helps if you fill out your signature line with what you have and what's been upgraded

Last edited by FiznUKa; 09-23-2017 at 09:59 AM. Reason: Addition
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Old 09-23-2017, 12:23 PM
sinapu sinapu is offline
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Any thoughts on where to start troubleshooting?
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