V1 P0315 Crankshaft Position (CPK)

[Robinjo]

Storing for later, need to check PCM C2#17 and #18

 

[Gtstorey]

So yours is different from mine. Mine is a 3 wire Hall effect sensor. Yours is a 2 wire inductive sensor.

You really need to dig out the actual wiring diagram, but it probably just runs from the sensor to the ECM.

You should be able to check the function of the sensor itself with a voltmeter to check for voltage when the engine is turning over.

https://carelectronix.com/answered-how-to-test-crank-position-sensor-practical-guide/#:~:text=Here%20are%20the%20steps%20to%20test%20a%202,multimeter%20to%20the%20other%20terminal%20of%20the%20sensor

.

 

[Ross]

Yes, PU is purple.
How does a 2 wire crankshaft sensor work?
2 wire crank sensor is an inductive type sensor which consists of a sensor magnet and winding coil and a toothed wheel. As the reluctor ring or the toothed wheel comes closer to the crank sensor, the magnetic field fluctuates as a result voltage is produced in the wiring coil.

So there is no 5V+ supply for this sensor, as it makes electricity by the crankshafts movement. Probably makes less than 5V, but I didn't measure it.

 

[Robinjo]

You really need to dig out the actual wiring diagram, but it probably just runs from the sensor to the ECM.

I did pull the wiring diagram. The route goes directly from the sensor to the C2 connector on the PCM. In the diagram, what does the yellow highlighted 'z' line mean? And the black triangle with exclamation point symbol next to the CPK view, what does that mean?

You should be able to check the function of the sensor itself with a voltmeter to check for voltage when the engine is turning over.

I'm planning to pull the sensor, check the Ohms on it and then do a little testing with a piece of meatal to see if the volts change. Then, if it passes those, test that the sensor is making voltage when the engine turns over.

Assuming all my stuff checks out and the sensor wires are good then PCM just thinks the CPK is not there. Can I just reflash my latest tune file where the PCM did think the CPK was there?

 

[Gtstorey]

I think the "Z" indicates a shielded wire, either as a twisted pair or actual foil barrier around the wires.

Make sure you are testing this as a two wire type ckp and not a three wire. I'm not sure a resistance test will work on a two wire.

I doubt your tune file contains the "learned" data for the ckp. I also think you are going to find that the ECM is seeing a signal from the CKP but doesn't trust it or has lost it's "compare" values.

 

[Robinjo]

I think the "Z" indicates a shielded wire, either as a twisted pair or actual foil barrier around the wires.

Make sure you are testing this as a two wire type ckp and not a three wire. I'm not sure a resistance test will work on a two wire.

I doubt your tune file contains the "learned" data for the ckp. I also think you are going to find that the ECM is seeing a signal from the CKP but doesn't trust it or has lost it's "compare" values.

One of the steps in the 2-wire diagnostic of a CPK it listed that the unit should give a resistance. I have the value wrote down at home, but it was a number. Then the next step was to check the wires. Lastly, was to check that the CPK would read a small voltage change if you waved a piece of metal close to the sensor head.

After I do all the testing, if it comes up ok on everything. What are my next steps to get the ECM to trust the sensor again? I didn't see steps to relearn the CPK, just that it needed to be completed.

Last thoughts, is this common for a ECM to stop trusting a CPK for some reason? I don't see a lot of posts about this, so I'm thinking no. If no, then I'm curious as to why my ECM decided to not trust the CPK again. I'm actually hoping my CPK is faulty and that would point me to a 'why'. If it's not, then I'm worried this will happen again somewhere where I can't diagnose it easily (like at GoblinFest.....).

 

[Gtstorey]

Most of the test I see for a 2 wire just check voltage while passing metal by the sensor, usually by cranking it. I did just find one that references a resistance test but it says to check the service manual for the correct resistance.

I could be wrong and it's a bad sensor. This is as much an art as science and guessing what the diagnostics aren't saying. I just typically start with the position that the DTC is correct in what it is saying until that doesn't fix the problem.

Next step when you get a good ckp, either the existing or new, is to relearn it. There should be relearn steps in alldata for your model but it may just say connect to scanner and relearn. I checked the list for my autel and it should relearn the 2006 Cobalt.

As far as why it needs relearning, beyond the issues of why it might have an issue with a relearn that I posted in #10, I don't know. Maybe you are getting noise on the wire because you routed it different. Maybe you bumped the sensor and its reading different. Maybe it picked up trash on the sensor or wheel. Maybe the ECM has problems. All you can do is get it going and see what happens.

 

[Robinjo]

Most of the test I see for a 2 wire just check voltage while passing metal by the sensor, usually by cranking it. I did just find one that references a resistance test but it says to check the service manual for the correct resistance.

I could be wrong and it's a bad sensor. This is as much an art as science and guessing what the diagnostics aren't saying. I just typically start with the position that the DTC is correct in what it is saying until that doesn't fix the problem.

Next step when you get a good ckp, either the existing or new, is to relearn it. There should be relearn steps in alldata for your model but it may just say connect to scanner and relearn. I checked the list for my autel and it should relearn the 2006 Cobalt.

As far as why it needs relearning, beyond the issues of why it might have an issue with a relearn that I posted in #10, I don't know. Maybe you are getting noise on the wire because you routed it different. Maybe you bumped the sensor and its reading different. Maybe it picked up trash on the sensor or wheel. Maybe the ECM has problems. All you can do is get it going and see what happens.

Thanks for the information, I really do appreciate it all!

For now, I'm going to move forward with diagnosing and see what I get.

 

[Robinjo]

Ok, got a little further along in the process but nothing points to anything suspect. I have continuity across the the wires from PCM C1 to the two end of the harness at the CPK sensor. #17 Purple and #18 Yellow test ok to their corresponding points at the end of the harness. Also, go the CPK out of the vehicle. On the 20k Ohms I get 0.92. Also, when checking the voltage when placing a metal (plyers ends) near the sensor head it gives a bit of voltage. When I pull the metal away, the reading drops to 0 volts. Next up is to put it all back together and see if I get voltage when the engine turns over to work the magnet in the CPK.

One miscellaneous thing, on the Fuse Block - Underhood C1 at position F3 (Circuit 150), this ground does not give continuity when attached to a know good ground point. The other 2 in this C1 do.... Not sure if this is related

 

[Gtstorey]

Need to find that ground in the wiring diagrams and see what it goes with. There are several grounds not needed. Or you can just ground it since I’m unaware of anything it will hurt, assuming you never removed and reinstalled any of the individual wires. Everything I’ve seen on any of the fuse box connectors that is black is a ground.

 

[Gtstorey]

I’ve been concentrating on your p0315 code and just troubleshooting shooting it. I’m not sure that that code is the problem for you no start problem. I think it should still start and run with that code active.

 

[Robinjo]

I did find an injector wire that pulled out of those stupid solder connectors. I pulled them all off and soldered them the correct way then with heat shrink tubes and electrical tape. It’s possible this was the culprit or just pulled out from messing around in the area.

Future builders, just solder the right way. While the heat shrink solder tubes are quicker, they are a pain in the end.

 

[Robinjo]

And….. Drago fires now! I believe the culprit to be the fuel injector harness connector (previously mentioned) to be the source. P0315 is still in the fault codes but the car starts. Loogle searches say that driving the car for a bit will potentially erase the code once the car learns the sensor again. Either that or I have to do some magic in a Tech2.

 

[Gtstorey]

We should have checked to see if it was firing at the beginning. If it was firing it was getting a crank signal. Lesson for next time.

I can bring my scanner over for the relearn or you can bring the car to me me if you need to force the relearn, if you don’t have the tech2 already. And HPT can possibly do it.

 

[Robinjo]

We should have checked to see if it was firing at the beginning. If it was firing it was getting a crank signal. Lesson for next time.

I can bring my scanner over for the relearn or you can bring the car to me me if you need to force the relearn, if you don’t have the tech2 already. And HPT can possibly do it.

I've heard HPT will do it but I may just have to work out a tie to swing by and see what your device can do. I'm just happy it's running right now as I was a little worried that GoblinFest was getting scrapped. I drove it to work today and the code is still there. I'm going to give it a few cycles to see if it learns the CPK again.
So strange it gave me a P0315 and not a Fuel Injector code.

 

[Gtstorey]

The ECM doesn't monitor several of the commanded things as well as you might expect. It doesn't know if coils actually have power to them for example.

 

[Robinjo]

So strange. I thought for sure that'd be one of the many things the vehicle looks for.