Saab 07 GM HFV6 - Camshaft Performance Issue w/ Waveforms

2007 Saab Aero 2.8 (B284L) aka GM HFV6 82k miles (this engine in the Cadillac forums is known for timing chain stretch)

Car threw a P0341 which is performance issue on bank2 camshaft position sensor. Being the car is old and a GM sensor was cheap, put it a new sensor reset ecu via tech2 and code came back. After much lurking on here and youtube picked up a hantek oscilliscope and got my waveforms. I am hoping that my initial thought that something happened to the reluctor wheel is wrong but here are my results. I added a shot of the camshaft and wheel in the upper corner of my photo. A video is also attached.

Video of wavform:


Video testing cam angle using Tech2:
Since the dtc code p0341 has been set for bank1, the ecu maybe running the stock values and that is why there is no change showing on bank1.

That little blip in the waveform is weird. Try clearing the codes and try running the cam test again with your scanner. But does this engine have any type of variable valve timing solenoids? Desired isn’t matching actual.

Can you post code setting criteria??

Hey Cheryl,

Yes, this engine has is VVT and has 2 timing solenoids. I'll give what you recommended a try. I also have to get a crankshaft and camshaft waveform to see if anything shows up with the timing.

Setting of code:
Enable criteria:
Engine running.

Fault criteria:
Signal corresponds to more than 13 pulses/less than 11 pulses from the sensor when the crankshaft has turned three revolutions.

I’d be checking the vvt solenoid for the bank that isn’t moving maybe it’s stuck

Cheryl that is a good observation I actually tested that vvt with the car off using the tech2 and I could hear the solenoid but that fact that it isn't changing could be because the car is running at default base timing since the code for the sensor has been set. Once the ecm sees that camshaft sensor on that bank is acting up its puts the car into base timing.

I'll be posting cam/crank waveforms tomorrow.

Based on the video, I suspect you have a reluctor wheel issue on bank two. I Painted up a screenshot for clarity:



From what I could see, the issue is with this specific cam pulse (the second long one) and no other. That makes me think that there's something wrong with the metallurgy of that specific tooth on the cam sprocket. In other words, the sprocket is not magnetically triggering the sensor correctly. When you look at a picture of the cam sprocket, you'll see what I mean:



An air gap problem is possible but unlikely, since the waveform problem only occurs in one spot. The sprocket or reluctor wheel may be bent, but that still adds up to a sprocket problem, IMO.

You can remove the cam sensor and visually inspect for damage to the reluctor wheel. However, even if you don't find any, that doesn't mean the reluctor is good. I've seen other reluctor wheels produce similar issues, and the only cure was replacement.

Thanks Tyler, I originally thought my reluctor wheel might have fallen off as these gm HFv6 apparently are prone to that. I am going to have to put a scope in the camshaft hole and see if I can see anything out of the ordinary.

The fact that a visual inspection might not reveal the problem is a bit concerning. I'll post back thanks for sharing that bit of knowledge!

Pulled the camshaft sensor to peer into the hole. On the reluctor wheel I see what looks like a burr on the long tooth. I can't tell how this happened but the burr is higher then the wheel, meaning when I touch it with a screw driver, the ridge is higher then the tooth. I thought originally the wheel might have had an outside coating fall off. I have attached a few of my photos and one of the a reluctor wheel looks like from an engine overhaul video.

Could that burr be what is causing the signal of the long tooth to show up no completed?

Hey cloves! Thanks for the update.

IMO, no, the burr you found doesn't account for the abnormal CMP waveform. From what I can see, the width of the burr is a fraction of the total tooth duration, and not enough to explain why most of the tooth is missing in the waveform.

However, if some thing HIT the reluctor tooth and caused the burr, then you might be onto something. As in, the impact created the burr and also changed the air gap for that specific tooth. That's purely speculation. :silly:

Either way, I still think you're down to sprocket replacement. I'm unfamiliar with the 2.8L version of the High Feature engine, so I'm not sure what's involved with that repair. I know on the 3.0L and 3.6L that sprocket replacement is POSSIBLE without timing cover removal, but risky. IMO, if you wanna repair this right, be prepared to replace all the timing components.

Tyler thanks again for again for all your feedback. I also feel the burr isn't really enough for the tooth to be missing on the waveform like that its minor. I decided rather crudely to test if that reluctor wheel was indeed off angle. I put a hard wire just shy of contacting the wheel and spun the crankshaft around. All teeth seem to be on the same plane.

I will start sourcing the parts and just do the timing chain while I open up the car since the chain on the Cadillac forums def seems to stretch early. From what I read online the LP9 (Saab 2.8L Turbo) is pretty much the same as the 3.6 aside from the pistons and crank.

I'll update this thread as I continue to make progress.