2005 GXP Codes

[redwingsfan34]

So how may of your remember me? :D

There is a 2005 GXP at, 99,000 miles, a local credit union as a repo for sale. I immediately went to check it out. Took it for a test drive and right away noticed an issue, it was running rough, i'm not an expert by any means, but it felt like it wasn't running on all cylinders. It smoothed out pretty quick though. It had an SES light, so I checked the codes. P0300, and P0315.
I don't know if the crankshaft position sensor could cause the misfires? Or if they are two completely different issues.

Ive searched a bit on the P0300 code but it seems to me like it could be a lot of things causing that.

Truthfully the codes have me a bit leery of it. But if I can get it for cheap enough even with a blown motor I'd be interested

As I'm not entirely familiar with the northstar, i figured I'd come say hi and see what you guys had to say about the codes.

Oh and if anyone cares the GA is long gone.

[crash93ssei]

Hey good to see you around again! Not too sure on the codes, but if the engine is bad, expect about $1,000 into finding a good one and a very not fun time swapping it. I can say that it will be worth it though and I would do it again in a heartbeat if I had the time and a place inside to do it.

[Archon]

DTC P0315
Circuit Description

The crankshaft position (CKP) system variation learn feature is used to calculate reference period errors caused by slight tolerance variations in the crankshaft, and the CKP sensors. The calculated error allows the powertrain control module (PCM) to accurately compensate for reference period variations. This enhances the ability of the PCM to detect misfire events over a wider range of engine speed and load.

The CKP system variation compensating values are stored in PCM memory after a learn procedure has been performed. If the actual CKP variation is not within the CKP system variation compensating values stored in the PCM, DTC P0300 may set.

If the CKP system variation values are not stored in the PCM memory, DTC P0315 sets.
DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0315 Crankshaft Position (CKP) System Variation Not Learned
Conditions for Running the DTC

DTCs P0335, P0336, P0340, P0341, P0385, P0386, P1372 are not set.
The engine coolant temperature (ECT) is more than 70°C (158°F).

Conditions for Setting the DTC

The CKP system variation values are not stored in the PCM memory.
Action Taken When the DTC Sets

The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

Conditions for Clearing the MIL/DTC

The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Inspect for the following conditions:

Worn crankshaft main bearings
Debris between the CKP sensor and the reluctor wheel
A damaged reluctor wheel
Excessive crankshaft runout
A damaged crankshaft--Refer to Crankshaft Balancer Cleaning and Inspection in Engine Mechanical.

Electromagnetic interference (EMI) in the signal circuit of the CKP sensor
The ignition switch is in the ON position until the battery has insufficient system voltage.
A powertrain control module (PCM) power disconnect with the ignition ON may erase the stored value and set the DTC P0315.

I would wonder why there would be a reason for a relearn.

[redwingsfan34]

Okay, not going to lie, that confused me a little bit.

Correct me if I'm wrong. But, that is saying the P0300 may be caused by the P0315? But it could be a lot of things that set off the P0315?

Can someone summarize that in a little easier to understand format? :D

[CMNTMXR57]

Why does it need to learn? To learn the individual engine/vehicle/part's tolerances. Not every N* is 110% perfect. There are some levels of variation. This is what it is learning. Then if it loses this stared variance, this code sets.

9 times out of 10, it's just built up crud/grease between the reluctor and the CKP sensor.