Hello all, I just installed a GM LS3 58x crate motor. The motor starts to stumble hard when trying to rev the engine "fast". I can slowly rev the motor to 4k with no issues while in neutral. my tuner was watching it, I drop about 1k everytime it stumbles. I keep getting a P0336 Crank sensor code no matter what I do fix the issue. I never had this issue when I had the previous LS3 24X motor in the car.

List of things checked,
1) New professional tune, I have used the same guy for a few years now, he is always spot on.
2) two different Lingenfelter boxes, both new and installed correctly.
3) four different crank sensors
4) I checked my stock crank sensor harness, here are the results.

I get good ohm on pin 12 of the blue pcm connector to circuit 1869 CKP of the crank sensor plug.

I get good ohm on pin 21 of the same pcm connector to circuit 1868 CKP low reference sensor plug.

When I check pin 2 of the same pcm connector to circuit 1867 12v reference, I only see - 2.763 with the key on to run, and the other end to the negative of the battery.


I have not checked the machined surface to the reluctor wheel yet, as you may know, there is not enough room to get a good look at the wheel to make sure I would be measuring correctly. At that point, if it is bad, the motor would need to be pulled anyways.

Tomorrow I am going to check straight from PCM on pin 2 Blue to see if I am getting a 12v signal. That would tell me there is a break in the wire to the plug someplace, or am I incorrect?

I would really appreciate any correct help with this. I'm about to pull the motor out and put my old LS3 24X back in...

 

Unplug the cam sensor connector and see if you now see 12 volts on the crank sensor reference circuit.…they share the same 12 volt feed…the cam sensor may be shorted…BTW, you should see less than 100mv’s on a sensor ground…you don’t check it using resistance testing unless you are just checking for a broken wire.

 

Will do, and yes I was just checking for broken wires at first, then values. I'll post back up later when I get the testing completed. Thanks.

I'm going to ask this only for learning purposes. If the can sensor is shorted, why would the engine start, and run smooth at idle and slow rev? Also, the Lingenfelter boxes shows that it is receiving good signal from both sensors.

 

Only the crank sensor is needed for the car to start and run…it is best to use a scope of the cam and crank sensor signal wires…check the cam sensor feed wire also…below is a cam-crank waveform from my 2008 LS3…58X crank and a 4X cam…both my sensors use a 5 volt reference and not 12 volts.

 

Unfortunately, I do not have a scope. My shop manuals show the crank to be 12v, I will have to look up the Cam sensor to be sure, and then will check at my harness for values.

 

If you are using the OE PCM both will be 12 volts….that is what your PCM is looking for with these 2 Hall Effect sensors…12 volts toggled to ground from the sensors.

 

Yes, still stock OE pcm. My other LS3 I had the 58x wheel swapped for a 24x wheel. If it wouldn't void the warranty, I would've done the same on this motor.

 

I'm not sure how these adapter harnesses work as I probably wouldn't touch your car if brought to me but your currently installed PCM is looking for a 24X and a 1X signal toggled from 12 volts to ground.

 

Ok, this is what my findings are.

Cam sensor unplugged, harness -2.673 at circuit C 1867 for 12v ref.

Cam sensor harness, 12v at circuit A 633, not circuit C 631 as the manual shows.

This is all with the key at run, not at start positions. Should I have someone craving the engine while checking the circuits?

 

The PCM is putting out 12 volts on the RED circuit 631 wire (C2 connector terminal 39 terminal C….like I said I don’t know if there is an adapter harness or some gizmo between the PCM and Cam sensor but if the wiring on those 3 wires are correct the Cam sensor pin out must match also for everything to work correctly.…disconnect this harness or whatever you have hooked up and see if you have 12 volts AT the PCM on both Cam and Crank sensors !!

 

Am only taking readings from the stock harness.



These pictures are of the cam plug.

 

Well I see 11.47 volts and I’m assuming that is terminal C…don’t know if you have an open (OL) on the signal and low reference…do you know how the cam and crank sensor works ??…if not you can’t diagnose it !!…when checking the low reference you DON’T use an ohm meter…the only time I use an ohm meter if it is spelled out in Service Info like fuel injector testing or CAN bus which is on the C6,7 and 8…one can also check the “signal” wire with a 12 volt test light…I see many issues on here with these engine swaps.

 

This is how my 2008 works…

 

This is what sets this DTC…GM doesn’t tell us what is “out of range” but sometimes you can use the 90-10 rule…the 12 volts should be at least be at 11.0 volts and the ground less than 1 volt…we don’t know if the PCM is looking at the rising or falling edge of those 2 signals…that is why a labscope is needed for this diagnosis.

 

That is not terminal C it's A as shown in the pictures.

 

Whether 12 volts or 5 volts that is fed into terminal A of the CMP sensor itself…I’d contact the manufacturer of that adapter…I don’t think I can offer you anymore help with this.

 

I'm only taking readings from the stock connectors from the car that come directly from the pcm, nothing else.

 

Well the only 2 readings you can check is the 12 volt reference and the low reference ground which I said should be less than 100 mv’s (0.1 volts) with ignition on or engine running…the signal wire is best checked with a labscope…with a scope you would make sure you see 12 volts and that it gets pulled fully to ground…from the OE harness to the sensor that is something you’ll have to check.

 

Ok. I find a scope someplace. Honestly, I'm about ready to pull the motor and just put a bigger cam in my other LS3. I have a complete cam package from Texas Speed that has been sitting here waiting to go in it anyways. I planned on doing it this winter as a spare motor incase something went wrong with the crate motor. If the car runs as should with the old motor, I can rule out the factory wiring.

That leaves me with a couple things to look at.

1) the computer just doesn't like something about the lingenfelter wiring/ box.

2) something is wrong with this brand new crate motor. When I go through the motor and hopefully find nothing wrong with it, I'll pull the crank and have a 24x installed.

 

So, I put the old motor back in, LS3 24X reluctor that I installed when I first built this motor a couple years ago. I also installed a bigger cam before putting it back in. It fired right up, no issues.

That leaves the following.
1) wiring in the car IS correct
2) both boxes are bad, or incorrectly pinned out (I think back to the 12v in the wrong position on the plug to the cam sensor)
3) the 58x reluctor spacing from the wheel to the machined surface is not to the dimension of should be
4) a combination of two