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I'd try Mobil 1 or Castrol Titanium synthetics with an AC Delco filter, what's the worst that can happen. The CELS stop.
Don't get me wrong Royal Purple is an exceptional oil but sometimes not for these cars.
I'd swap out the Wix filter for sure for the Delco, same reason as above.
 

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I've had 263,000km of good luck with Lucas synthetic oil as well - and always a quality filter, never cheap out on the filter. Lucas has never let me down with any of their product - the oil is a bit hard to find these days as not too many retailers, in my area at least, carry it.
 

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Discussion Starter · #23 ·
Another update to the mess; got the oil changed with an ACDelco filter and Castrol GTX 5w-30, code still pops consistently and the counts are still off on the single sensor, I've already scheduled the 19th with the base's auto hobby to let them look at it, see if they have better luck than myself.
 

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If it is a sensor go with the OEM sensor, plenty of threads on here about after market sensors giving these car fits. Should be a Bosch sensor.
 

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Discussion Starter · #25 ·
Yup, I put a Bosch sensor in it, doesn't seem to have helped the situation however.
 

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Not trying to turn this into another oil thread, but run Castrol GTX high mileage 5W-30 in the G8 with zero adverse effects to date. Always keep the oil level full and regularly change both the oil and filter long before it's required by the oil life monitoring system. Is P0391 the check engine light referenced in post eighteen?
 

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Discussion Starter · #27 ·
It is indeed, and I've been changing at 3000 miles religiously, and the last oil change was at 1000 miles to clear the royal purple and put Castrol GTX in it, couldn't find any High mileage.
 

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Normally change it about every 5,000 miles and have always found it difficult to justify the cost of Royal Purple. However, that's neither here nor there as most people have a preferred brand. Does the the check engine light illuminate while driving after a few start cycles? Meaning start the car, no code. Drive a few days, start it and immediately the light illuminates? Does it ever clear itself after a few start cycles?
 

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Discussion Starter · #29 ·
At the time of that post, it would come in and go out, but now it is constantly lit up almost no matter what I do. I can clear it, and then it will be back on the next start up after I put the car in gear.
 

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Discussion Starter · #30 ·
Update for multiple sensors; I've got low voltage codes for Oil pressure, both sides actuators, and camshaft position sensor, I will be parking the car until the 19th when I have time to properly look at it.
 

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Best of fortune getting the various issues resolved and concur it's best to park the vehicle until further analysis can be done. Don't have any new input to add, but will continue to track thread updates.
 

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Discussion Starter · #33 ·
Early morning(for me) update; Checked every ground I could think of(Not very many if I'm honest), looked at the fuses to see if any had blown and I couldn't see one, checked a few connections and none were loose. So I put a multimeter to the car, turned it on as well as every single accessory on, wind shield wipers, heated seats, bright lights interior lights, etc, and watched the voltage, 14.5-14.7 the entire time, let it sit for a bit and cleared codes.

Started up no issues, let it warm up and tentatively moved around the parking lot, still nothing. Went ahead and drove it around base, seemed like the car fixed itself, parked it, turned it off and let it sit, came back a few hours later and started it back up and the P0391 came back, but none of the other codes set, we'll see later tonight if they come back again, I'm not entirely sure what else too look at, but if anyone has wiring diagrams for the Camshaft position sensors, where they ground etc, or just an entire location list of grounds, I would happily use them right about now lol.
 

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Discussion Starter · #34 ·
Seems my insomnia hits when the car gives me a multitude of issues, not to mention a full lock-down due to recent events. How quaint.
 

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That particular fault code (as well as many others), are classified as B rated codes. Anytime you hook up a scan tester to view (any an all fault) codes captured an then reset, any B rated fault code "will not" reappear until 2 consecutive start/run cycles have happened. So if you get that P0391 on your second start/run cycle, the same item must have been detected with the same problem on its first start/run cycle after you performed a reset.

All 3 wires for each of the cam position sensors are hard wired to an from the ECM. Pin 1 at all 4 connectors is the ground return, an it is grounded inside the ECM. Pin 2 at all 4 connectors show that they have about 4.8 volts from the ECM. Pin 3 at all 4 connectors is supplied with a 5 volt reference from the ECM. Check for continuity of the ground wire going back to the ECM on pin 1 with the ignition off. Then verify the voltage readings on pins 2 an 3 with the ignition in the full on position (using an alternate ground location as well as using pin 1 as the ground source).
 

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On the 3.6 sometimes if there is to much camshaft endplay you will lose cam signal because the cam walks away from the sensor and wont read. There is a service bulletin on this issue. I will try and find it when I go to work tomorrow.
 

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Discussion Starter · #37 ·
Somewhat disappointed but expected update; started the car up 20 minutes ago, the last shut down being somewhere around 10am, it is currently 1744. All the codes I could ever pick from, I do have a second thread asking about the other issue but I will combine the two from here on as I believe they are related in some way.

P0391 Camshaft position (CMP) Sensor performance bank 2
P0305 Cylinder 5 misfire detected
P0303 Cylinder 3 Misfire detected
P0300 Engine Misfire detected
P0121 Throttle Position (TP) Sensor 1 Performance

Are the codes I got from initial start up, safety mode was enabled and traction control was turned off, likely due to the misfires, which was expected. I checked voltages while it was warming up via a multimeter and the DIC, both read 14.7. I am starting to suspect an ECM issue, due to getting it programmed recently as January due to a throttle position sensor replacement, I will likely bring it back to the Dealershop that performed the maintenance yo see what their protocol is on it, as to see if they are willing to own up to being the possible cause to potential ECM issues.
 

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Discussion Starter · #38 ·
As a side note; due to recent events in the area around me, the local auto hobby shop I do my DIY work out of is closed I won't be able to dig into the car myself until the 30th. Bummer and bad timing.
 

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Discussion Starter · #40 ·
Good information on that TSB, thank you Wild.

As I'm not ruling any odd behavior on the car's part being a potential evidence or otherwise, we've got a few possibly unrelated updates. I went to continue troubleshoot the car further, watch various systems on it and see if any others are giving codes and issues, when I turned the car on it didn't give me any issues CEL was the same, no rough running however, the DIC on the other hand applied the lower half of the screen to the upper half, and the center counsel went blank when I attempted to adjust the A/C.

Possible more evidence toward the issue being computer related. Car is still being parked until I can figure it out however, or until I get a chance to go to a dealership or reputable shop.
 
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