calongo_SS

iTrader: (7)

I tried this in the PCM section but it hasn't got much attention, so I'll try here.

The car is a 2001 camaro, it has been cammed for quite a while.
I've decided to go a different direction and change to a much smaller cam.

Cam install went fine, nothing unexpected.
Try to start the car after the install, battery is dead (car's been sitting a week or so). Put a different battery in and the car cranked and back fired out the exhaust a few times. Turned key back to off, gave it a little gas and it fired up. Car idles pretty smooth but tach is dead stays at 0 rpm & throws a P0343 (camshaft position sensor circuit high). Car seems to do this pretty consistently, it will not start, turn key to off, then it fires.

So far I have hooked a volt meter to the pin @ the PCM for the cam pos. sensor while the car is running. It does indeed stay high, a constant 11 V.
Today I changed the sensor. While i had the sensor out I used a mirror and looked down the hole and could see that the cam does indeed have a reluctor wheel on it. I tried to move the cam gently with a screwdriver to see if something was left loose and the cam was walking. I could not move the cam.

This is not my first cam install, but this is the first time I've seen this come up. What could be causing it other than cam walk or a faulty reluctor wheel on the cam?

eallanboggs

iTrader: (1)

Try turning the crank over by hand while monitoring the voltage at the pin on the PCM for the cam sensor as you just did. If you were to monitor it with a labscope or "O" scope while the engine is running it would be a square wave, but since you will be turning the engine over very slowly by hand you will only be looking for a transition from 0Vdc to Vcc.

calongo_SS

iTrader: (7)

Shouldn't I be able to see it switching rapidly on the multimeter w/ the engine running? Or at least shouldn't the MM be trying to get on the right range instead of staying @ 11V constant?

01redws6ta

which pin are you checking at...C1 connector pin 73 is the signal wire terminal. Duty cycle on this circuit with engine running should read 45-55%. Easiest way to test would be to either backprobe it or cut the wire and leave enough to heat shrink splice it back together. You need a DMM which reads duty cycle of course.

calongo_SS

iTrader: (7)

Yes, C1 pin 73. I was just reading DC volts, I should be able to see it switching or, at least seem some fluctuation in the voltage level. I could possibly bring a scope home from work, but I don't really see the point. The PCM is saying the signal is staying high, the DMM says the signal is staying high, I'm sure the scope will show a straight line, not a square wave. Might be worth a shot though before I tear it down again.

01redws6ta

If it is indeed staying high, then it could possibly be that circuit shorted to voltage or possibly the low reference circuit with an open. I would test these circuits. You have the manifold back on now then?

calongo_SS

iTrader: (7)

Yes manifold is back on.
Are the references you are referring to the other wires going to the sensor? I assumed one is a 12 V (high signal), one is a ground or some voltage lower than 12 (low signal), and the other is the return to the PCM.
My thinking is that if the 12 V was shorted to ground somewhere I would not see 12 V on the signal wire. I did mark the sensor's wiring loom behind the head w/ some white tape so I could access those wires again if needed. I can inspect the wires to see if they are shorted to each other somewhere, but at this point I'm leaning towards something wrong with the cam or something I messed up under the timing cover. I just don't see what I could have done wrong other than leaving bolts loose which is something I know I didn't do.

eallanboggs

iTrader: (1)

Your DVM can't switch fast enough to see the voltage change you're looking for with the engine running. That's why you need to turn the motor over by hand or use a scope to check it in real time. You must have a DTC that is telling your CMP sense wire is a constant 12Vdc. Have you looked up the troubleshooting procedure for that DTC. It's in Helm or Mitchell or Alldata.

eallanboggs

iTrader: (1)

P0343 DTC
No signal from CMP for 200 revolutions
Enable condition:Engine speed >600 RPM
MIL illuminates after 2 drive cycles

Open or shorted B+ between CMP and PCM
Open/Faulty CMP sensor
Open between relay and CMP(ref. voltage)
Missing pin on electrical connector
Open or short on wiring harness

That should help get you started. Now it's the DVM and the process of elimination.

calongo_SS

iTrader: (7)

Yeah, I've looked up the trouble shooting procedure. The problem with that is; that is for a car that had this problem come up out of the blue. This problem started immediately after I swapped cams, I was hoping to get lucky and the problem be the sensor. I'll check it how you recommend, turning the motor over by hand. It's got to have something to do with the cam install, or the cam itself.

RooRnZ28

iTrader: (14)

did you change your timing chain at all? if you changed the timing chain, especially to a double roller, then that is your problem.

calongo_SS

iTrader: (7)

Not cam walk. The timing cover is off. I re-torqued all the cam gear bolts & retainer plate bolts and not one of them budged.
I pushed and pulled on the cam gear and it doesn't budge.

No, it is the same LS2 timing chain that was on the car before I swapped cams.

calongo_SS

iTrader: (7)

Well,
I decided to talk to an expert. I called Wheel 2 Wheel and talked to Kurt.
First thing he asked me is if XXXX ground the cam.
Of course, it is. He recommended pulling the cam and mic'ing the reluctor ring and comparing it to the old cam. They just had a car come through with almost the same problem and that was the cause. He also said he's seen a cam from them where the 2 half moon shaped reluctor rings were backwards.
I'm not going to mention the cam company here until I know for sure what the problem is and how they handle it.

calongo_SS

iTrader: (7)

Here's some pics. I need to find out what the tolerances are, or hopefully someone can tell me just from looking that it is bad. I don't have a nice pair of calipers to get actual measurements, but you can certainly see the difference between the cams using the cheapo ones I have.

Stock GM cam on the right, new cam on the left. The cam that came out of the car is identical to the stock cam in the area of the reluctors as far as I can tell.

Rotated 180 deg


Calipers were set and locked in on the new cam and then compared to the stock cam. These pictures are of the stock cam.
O.D. Of the ring. This one's kind of hard to see, but it's ~1/16" larger than stock judging by eye.


The width of the rings are considerably larger on the new cam.

tjwong

Did you fix your cam sensor issue? I am having the same issue, cam reluctor looks the same as the the cam you just removed. But I have used several cams using the very same reluctor and have never had a problem. In fact I have installed at least 10 of these cams using the same cores and never had a problem until today with a 1998 C5. Funny thing is that the engine started immediately upon cranking over. It wasn't until after it warmed up that I encountered a problem when trying to start it, the thing cranked over and over and burped out of the exhaust until it would figure out where number 1 is, then it starts, but throws P0343.