2010 VW Jetta TDI P0651 fault when vehicle parked on incline/hill

[TheresaM]

Glow plug light flashed with check engine light at initial sequence for start. Coded two faults P0651 (sensor reference voltage B circuit) and P0322 (engine speed imp. circuit no signal). Mileage on vehicle 180,251. Car towed and VW dealer replaced engine speed sensor. Car ran fine till about the third time I was ready to run an errand and the glow plug light flashed with check engine light. Car towed to VW dealer. What we are able to deduce is it's intermittently coding P0322 (engine speed imp. circuit no signal) fault only when vehicle is parked on roughly 15degree incline (same incline as my driveway). Even then the mechanic noted the fault ultimately went away in a few minutes. Mechanic did multiple 10 minute trips and could not reproduce the fault. Given it's positional, the mechanic thinks this may be moisture triggering a short. But they would need to pull apart the harness to find it and even then can't guarantee they will find the shorted wire(s) or if other internal components may be damaged as a result of the initial short. If they can't find it and need to replace the entire harness could run me more than the car's value.
Has anyone run into a positional, intermittent P0651 fault previously or has had the fault triggered by moisture? If so, what caused the water intrusion? Windshield gasket failure, or other? I would think if it's a positional, intermittent fault triggered by moisture on a vehicle with very limited movement since faults started (max travel time 20-30 minutes) then we should only be talking about a few corroded wire leads at worse case versus the need to replace an entire harness. Does this make sense or is there something more intrinsic to this Jetta TDI build that would complicate this repair?

Edit: Water intrusion not evident nor completely ruled out. No corrosion of connections or grounds observed. Fault only able to replicate when vehicle parked for a period of time on an incline.

 

[JELLOWSUBMARINE]

Got a sunroof? moist caepet? corroded grounds and or connections?

 

[TheresaM]

@JELLOWSUBMARINE, excellent questions. No sunroof. Front floor mats were dry. Didn’t think to check them all.
The connections and grounds don’t know. But I asked the mechanic if it was a true P0651 fault and they said yes. So I suspect we should find some corrosion on the leads/connections or ground if theory that it is a moisture issue is true.

 

[JELLOWSUBMARINE]

Grounds/connector corrosion seems very prevalent.

 

[TheresaM]

Grounds/connector corrosion seems very prevalent.

Where in the engine compartment is it most common? Would like to narrow a thousand wires to something more historically probable if possible.

 

[JELLOWSUBMARINE]

I've never encountered this but seen multiple threads on it. I dont know much about the sedan but the JSW w/sunroof, corroded grounds are typically reported around the a and b pillar.

When you mentioned engine compartment it made my wonder about one of the main big fuses with an arcing issue. I beleive there is an upgraded fuse fix.

 

[TheresaM]

Just spoke to the dealership, no corrosion on connections or grounds. They didn’t see any signs of water intrusion but are not completely ruling it out. Nor do they see a water test as value added. I will update the original post and title accordingly.
Their proposal is exploratory to find the short by opening up the 5 wire harnesses. My vehicle needed a central wiring harness (for fuel temp sensor) repair a few months after purchasing new (Nov2010) because it was run too tight around the engine cover causing chafing on the fuel line.
So I asked them to check for other signs of stress and chafed wiring.

 

[TheresaM]

Spoke to the dealership yesterday. They didn’t see any signs of stressed or chaffed wiring around the car. The fault even the one time they were able to reproduce it did not stay on long enough to find the problem. The battery will be 5years old next month and reading 11.4volts. We are betting the car may be throwing this transient code as the battery is nearing the end of its life. Haven’t had that happen before (I am the original owner) but it is getting colder outside here.