Intermittent P003A and P2599 on 2016 GMC LML Duramax

jahoffma

New member
Sep 9, 2025
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1
Minnesota
I have a Topdon Diagnostic tool to read DTCs, monitor operating conditions, perform diagnostic tests and reset DTCs when a problem / issue is corrected.

I have had both P003A and P2599 DTC codes trip the MIL light several times in the past 2 weeks - recorded as Turbo Vane Position Learn Pass & Failure. Eventually, the MIL lamp resets (after 20 successful vane position learn events). In each case, no towing/heavy load situation - once on startup, twice while driving at highway speed (60-65mph) on level road (as is most of Minnesota's highways). No other DTCs or abnormal items found during system component scans/DTC interrogations. The truck has 167,000 miles - 80% of which are highway speed (60 mph or higher). This is my second Duramax.

Diagnostic procedure for P003A indicates correcting P2559 condition first.

Information gathered from scan tool:
- Operating conditions (freeze frame data) is normal / expected - everything is within standard operating parameters.
- Monitoring the Desired Vane Position and Vane Position Sensor data (and graphs) while driving in town (0-35 mph) and highway speeds (55-75 mph), both the desired and sensed positions track very tightly - very minimal variance until an acceleration, load (slight uphill/downhill) or deceleration condition occur...then the desired position change value slightly leads the sensed position, but it's only momentary (expected behavior). The Sensed Position catches up immediately.
- Vane position sensor voltage is also operating within normal/established min/max values, and the graph line tracks very tightly with the position graph lines.
- Commanding the "Learn Procedure" to increase and decrease vane positions (during idle) by 10% increments up to and back down from 100% completes successfully.

I am aware there are 4 general conditions that set these 2 codes:
- Problems with the Vane Position Sensor
- Problems with the Vane Position Solenoid
- Sticky Turbo Vanes
- Electrical Connection (damaged wires / faulty connections)

I have acquired both the OEM replacement sensor and solenoid. The sensor is a relatively easy task, whereas the solenoid is a little 'more involved' activity. However, I don't particularly care for 'rip and replace' by 'trial and failure" methods since the DTCs self-cleared and commanding vane position learn tests have passed. Also, I'm not terribly excited about the idea of removing the Turbo to examine the vanes -especially if this is not a high-frequency condition - due to the intrusiveness and effort just weeks before I'll be driving a long distance (2k miles round trip).

Looking for insights, advice, experience with similar conditions before just 'diving in head-first'.
 

Ron Nielson

Active member
Oct 11, 2009
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231
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Berryton, KS
Take a look at the attachments, which are specifically for my 2008 LMM. In particular, look at the Diagnostic Fault Information chart from P003a and the information in the P2599 document. See what they have in common. That's where I would start, before changing any parts.
 

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  • P003a new ALLDATA diy.pdf
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  • P2599.pdf
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jahoffma

New member
Sep 9, 2025
3
0
1
Minnesota
Thanks, Ron! I do have a subscription to the AllDataDIY site and have poured thru the direct and related docs/info there on these two DTC codes (forgot to mention that in my original description). I haven't found that specific PDF you posted for P2599 - that's very helpful and some of the insight I am seeking - something not covered in standard procedure docs. I'll check for chafing and clearance and let you know what I find.
 

jahoffma

New member
Sep 9, 2025
3
0
1
Minnesota
Ron - the 2016 harness appears to be routed slightly different, so it has plenty of clearance from the EGR. However, it does have some pressure - no chafing, from the adjacent pipe.
 

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