V1 P0315 Crankshaft Position (CPK)

[Robinjo]

Started the Goblin this morning to warm up before heading to work and the engine cut out, would not re-fire (but turns over) and gave me a P0315 Crank Position (CKP) System Variation. I'm going to make sure that it didn't come unplugged, check the fuse box connection and that I didn't blow a fuse when I get home this afternoon but the AllData site mentions potentially needing to do a Crank Position Sensor Relearn (up to 5 times). I'm looking into this further but just wanted to throw this up here to see if/how anyone else performed this task.

Context: I juts reinstalled my engine and transmission. It started last night and ran for about 30 seconds, before I shut it down. Started this morning as well and ran for abut 5 minutes. Engine cut out on it's own and would not restart but will turn over. I can hear the fuel pump priming and the throttle does respond to inputs from the pedal. I didn't clear the code and try it again.

Any and all suggestions are welcomed.

 

[Gtstorey]

Alldata should have the steps to trouble shoot that code but some of the older diagnostic steps can be hard to follow.

My Autel scanner should be able to perform the relearn if it doesn't require inputs the goblin doesn't have such as perking brake signal.

HPT may be able to do the relearn but it typically won't give you the feedback needed to help figure out how to perform it correctly.

That said, not sure why it would need a relearn from just pulling the motor, so it is probably a wiring issue.

 

[Robinjo]

....so it is probably a wiring issue.

I think this is the problem really, I was just trying to gather all the information I could before I get home tonight.

 

[Robinjo]

Can the engine start and run without the Crankshaft Position Sensor hooked up? Just curious about it starting a couple times and then just dying and not restarting.

 

[Gtstorey]

I think some vehicles with both crank and cam position sensors can run without one of them. It can use the cam position to determine crank position, after it determines whether it is on compression stroke. This is why if it loses one of the sensors, it can be slow to start until it determines which stroke it is on. This probably doesn't apply to all vehicles and I don't know if it applies to the Cobalt.

 

[G Atsma]

The LS V8 family will run without the cam sensor, but will take a few attempts at starting until the ECM figures out where the crank is.
It will NOT run without the crank sensor.

 

[Gtstorey]

The LS V8 family will run without the cam sensor, but will take a few attempts at starting until the ECM figures out where the crank is.
It will NOT run without the crank sensor.

This may be true on all of them. I knew it could run on one of them, I wasn't sure on the other.

 

[Robinjo]

Ok, sounds like something either came loose or the sensor failed. I'm basing this because it ran multiple times and then cut out (while running).

This gives me more information to consider while looking over the vehicle tonight.

 

[Robinjo]

Testing the crankshaft position sensor (CPS), a video online showed that the negative side of the CPS should give continuity when the other side is to a good ground. Testing this gave no continuity.

Next I moved to the fuse box as I saw another post that the X1(?) should have a ground going to the CPS. Testing grounds and this one does not give continuity to ground. The black wire right above my thumb.

 

[Gtstorey]

You really need to look up the wiring diagram for your model but what you describe doesn’t match the diagrams for the newer models. You probably should have a 5v coming from the ECM, a ground through the ECM, and a signal from the ckp to the ECM. You should check these at the sensor connection or by back probing the ECM connector. And the ckp sensor is likely grounding through the ECM X1 connector not the fuse box X1 connector which it appears that you are holding in the last picture.

Reading the service manual for the newer models makes it sound less likely that it’s a wiring issue unless it is getting interference. It sort of reads like once the code is set it won’t work until the relearn even if you correct a problem. Did you disconnect the power with the switch on or leave the switch on and run the battery low?

 

[Robinjo]

Reading the service manual for the newer models makes it sound less likely that it’s a wiring issue unless it is getting interference. It sort of reads like once the code is set it won’t work until the relearn even if you correct a problem. Did you disconnect the power with the switch on or leave the switch on and run the battery low?

I’ll pull the crankshaft position sensor and test it out. Would the cpk relay also be suspect?

Are you saying a relearn is needed regardless of anything else?

When you say ‘switch on’ do you mean key in the ignition switched on? If so, no. No key in the ignition when I took it all apart or disconnected the battery. When it died this morning it wouldn’t restart, but turns over the engine/starter. In that situation, yes the key switch was on.

 

[Robinjo]

You really need to look up the wiring diagram for your model but what you describe doesn’t match the diagrams for the newer models. You probably should have a 5v coming from the ECM, a ground through the ECM, and a signal from the ckp to the ECM. You should check these at the sensor connection or by back probing the ECM connector. And the ckp sensor is likely grounding through the ECM X1 connector not the fuse box X1 connector which it appears that you are holding in the last picture.

Yes, this was the fuse box X1, not the ECM X1. I’ll look up the diagram on AllData tomorrow.
I don’t understand back probing. Are you saying to find the right circuit via the diagram, then check for continuity from the wire listed in the diagram to the sensor?
Why am I not getting continuity from the negative side of the sensor harness to a good ground?

 

[Gtstorey]

I’m not aware of a ckp relay on the newer cars, and I wouldn’t expect the older cars to be that different but maybe they are. If you ckp sensor only has three wires to it I’m pretty sure there are only the 5v, ground and sensor signal.
Beyond that, all I know is what is on the page that I posted and reading between the lines. It sounds like if you get that code either it no longer has the learned values in the ECM or it has a reason to doubt them. That code isn’t what you would typically expect from a wiring problem which would be p0335, p0336 or p0338.

 

[Gtstorey]

Yes, this was the fuse box X1, not the ECM X1. I’ll look up the diagram on AllData tomorrow.
I don’t understand back probing. Are you saying to find the right circuit via the diagram, then check for continuity from the wire listed in the diagram to the sensor?
Why am I not getting continuity from the negative side of the sensor harness to a good ground?

Again all I have is the newer model diagrams so there is a slight chance yours is different.
But
The ground for the ckp runs through the ecm and might not ground if the ECM isn’t plugged in and powered up. Back probing is checking circuits by probing the back of the connector with it connected. On some of the connectors you may have to use a piece of mig welding wire or a sewing needle to reach metal to make the connection. Or you can use the needle to pierce the wire near the connector.

 

[Robinjo]

Again all I have is the newer model diagrams so there is a slight chance yours is different.
But
The ground for the ckp runs through the ecm and might not ground if the ECM isn’t plugged in and powered up. Back probing is checking circuits by probing the back of the connector with it connected. On some of the connectors you may have to use a piece of mig welding wire or a sewing needle to reach metal to make the connection. Or you can use the needle to pierce the wire near the connector.

I did test all this with the fuse box and ECM disconnected. And with the negative cable off the battery. I’m going to look up the diagrams tomorrow. Before putting it all back together to check the connectors with power, I’ll check the cpk sensor resistance and wire (from diagram) continuity.

 

[Gtstorey]

I just checked the diagnostic steps for the ckp wiring codes that I listed above and it does indicate that you should have less than 1 ohm of resistance between the sensor harness low reference terminal 2 and ground with the ignition off. What were you grounding to when you checked it and what did you mean by the other side in post 9.

Everything besides the ckp sensor will have to be connected to test this.

 

[Robinjo]

I just checked the diagnostic steps for the ckp wiring codes that I listed above and it does indicate that you should have less than 1 ohm of resistance between the sensor harness low reference terminal 2 and ground with the ignition off. What were you grounding to when you checked it and what did you mean by the other side in post 9.

Everything besides the ckp sensor will have to be connected to test this.

I didn’t check ohms with everything disconnected, just continuity. According to the video I watched one of the two wires is a ground and should have beeped. Other side post #9: I clipped ‘other side’ to my ground lug under the fuse box and probed the two terminals in the plug that attached to the CPK.
However, I did all this with the negative battery cable, fuse box and ECM disconnected.

 

[Gtstorey]

Virtually all engine sensors ground through a bus in the ECM. GM called it low reference in some years.It’s a “cleaner” ground point that the ECM uses to measure signals against. Sensors are rarely, if ever, grounded directly to “chassis” ground. If the ECM is unplugged the sensor won’t connect to chassis ground. The ECM is ground bus is connected to chassis ground so if the ECM is connected, the sensor should see ground. But be careful on just relying on the beep. There can still be problems with the circuit so even if you get a beep you should still follow up with a resistance check or even a test light to confirm it can actually carry useful current.

 

[Robinjo]

Thank you for the extra context into the GM CANBUS system, especially with sensors. My past car bobbies were late 80's to mid 90's Honda's, so they didn't have the whole array of sensors and ECM checks. It would check some things, but not to the extent that these do.

The video I watched about cpk sensors did not mention all the extra information, but it may have just assumed you were checking it all with the whole system hooked up. The video did go into resistance and voltage checks as well. I just though I had already found my problem based off the fuse box X1. Back to the researching.....

 

[Robinjo]

Jumping into AllData this morning and here is the connector view of the CPK sensor. Just to confirm, PU means 'Purple', correct?
In this diagram below, is 574 CPK Sensor Low Reference considered the ground and 573 CPK Sensor Signal the 5V power?