Testing LML VPS to ECM

19trax95

New member
Jun 30, 2021
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I'm helping my buddy out with his 2012 that he's having some issues with.

The turbo is seemingly stuck with the vanes open. Scan tool data shows the commanded vane position is 95% at idle but the actual vane position sits around 2% no matter what. I can command the vanes to move, and the ecm command matches what I enter, but the vanes still don't move obviously.

Verified the position sensor works, and it does. He installed a new garret vane solenoid since he thought that was the cause. That didn't fix anything. Also did the pig tail for the vane solenoid.

My thoughts are either the turbo vanes themselves are stuck, or there is an open in the harness from the vane solenoid connector to the ecm. I would tend to lean against the turbo itself, since it is new as of 2 months ago (granted that really means nothing). It also seems to have been an intermittent issue. It worked for a while, then stopped, then started working again, now it doesn't work at all.

I can't access any diagrams past the LMM motors through work, since I only have access to the medium and heavy duty side of things, and haven't been able to find anything solid online.

Does anyone happen to have an ECM connector pin out diagram for these LMLs? Or even just know which pins on the ecm connector are the vane solenoid control circuit?

Thanks for any help.
 

juddski88

Freedom Diesel
Jul 1, 2008
4,656
120
63
Chesterfield, Mass.
If the scan tool does not read an amp load from the solenoid circuit, then it's the solenoid or an open. If it does, then likely it's the unison ring sticking.